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• Working with Sub-Optimal Disk Configurations (Making the best of what you’ve got)

  - by Jonathan Kehayias

  This is the first post in a what will be a series of posts on working with a sub-optimal disk configuration to squeeze as much performance out of it as possible.  You might ask what a Sub-Optimal Disk Configuration?  In this case it is a Dell Powervault MD3000 with 15 Seagate Barracuda ES.2 SAS 1 TB 7.2K RPM disks (Model Number ST31000640SS).  This equates to just under 14TB of raw storage that can configured into a number of RAID configurations.  In this case, the disk array...(read more)

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• SQL SERVER – Iridium I/O – SQL Server Deduplication that Shrinks Databases and Improves Performance

  - by Pinal Dave

  Database performance is a common problem for SQL Server DBA’s.  It seems like we spend more time on performance than just about anything else.  In many cases, we use scripts or tools that point out performance bottlenecks but we don’t have any way to fix them.  For example, what do you do when you need to speed up a query that is already tuned as well as possible?  Or what do you do when you aren’t allowed to make changes for a database supporting a purchased application? Iridium I/O for SQL Server was originally built at Confio software (makers of Ignite) because DBA’s kept asking for a way to actually fix performance instead of just pointing out performance problems. The technology is certified by Microsoft and was so promising that it was spun out into a separate company that is now run by the Confio Founder/CEO and technology management team. Iridium uses deduplication technology to both shrink the databases as well as boost IO performance.  It is intriguing to see it work.  It will deduplicate a live database as it is running transactions.  You can watch the database get smaller while user queries are running. Iridium is a simple tool to use. After installing the software, you click an “Analyze” button which will spend a minute or two on each database and estimate both your storage and performance savings.  Next, you click an “Activate” button to turn on Iridium I/O for your selected databases.  You don’t need to reboot the operating system or restart the database during any part of the process. As part of my test, I also wanted to see if there would be an impact on my databases when Iridium was removed.  The ‘revert’ process (bringing the files back to their SQL Server native format) was executed by a simple click of a button, and completed while the databases were available for normal processing. I was impressed and enjoyed playing with the software and encourage all of you to try it out.  Here is the link to the website to download Iridium for free. . Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• Disk utility running for a long time

  - by Nik

  I had a spare, old external usb hard disk which stopped working long time back due to improper removal of disk. I tried fixing it in windows (when I did not have ubuntu yet), however I couldn't fix it. So I tried formatting the disk and creating a new partition using the disk utility in ubuntu. However it seems to keep running without any indication of the progress or whatsoever. I have no idea what is happening. I have attached a screenshot below to show what I mean. As you can from the screenshot above it seems to be working on it but no indication on the progress or what it is doing. Any attempt to exit it or do any other task like safe removal or format partition leads to the the following dialog box. What should I do? Wait or restart the computer..???

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• Changing Disk Allocation for Ubuntu on Dual-Boot System

  - by OtagoHarbour

  When I first installed Ubuntu, I had a new PC with Windows 7 installed. It was my first installation of Ubuntu so I only allocated 45% of the disk for Ubuntu. Now I find that I have been using Ubuntu exclusively so I would like to change the allocation of the disk so Ubuntu has say 75% of the disk and Win. 7 25%. Is there a way to do this without reformatting the disk. I am using Ubuntu 11.10 with Gnome. Thanks, Peter

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• SQL Server 2005 standard filegroups / files for performance on SAN

  - by Blootac

  I submitted this to stack overflow (here) but realised it should really be on serverfault. so apologies for the incorrect and duplicate posting: Ok so I've just been on a SQL Server course and we discussed the usage scenarios of multiple filegroups and files when in use over local RAID and local disks but we didn't touch SAN scenarios so my question is as follows; I currently have a 250 gig database running on SQL Server 2005 where some tables have a huge number of writes and others are fairly static. The database and all objects reside in a single file group with a single data file. The log file is also on the same volume. My interpretation is that separate data files should be used across different disks to lessen disk contention and that file groups should be used for partitioning of data. However, with a SAN you obviously don't really have the same issue of disk contention that you do with a small RAID setup (or at least we don't at the moment), and standard edition doesn't support partitioning. So in order to improve parallelism what should I do? My understanding of various Microsoft publications is that if I increase the number of data files, separate threads can act across each file separately. Which leads me to the question how many files should I have. One per core? Should I be putting tables and indexes with high levels of activity in separate file groups, each with the same number of data files as we have cores? Thank you

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• Very slow write performance on Debian 6.0 (AMD64) with DMCRYPT/LVM/RAID1

  - by jdelic

  I'm seeing very strange performance characteristics on one of my servers. This server is running a simple two-disk software-RAID1 setup with LVM spanning /dev/md0. One of the logical volumes /dev/vg0/secure is encrypted using dmcrypt with LUKS and mounted with the sync and noatimes flag. Writing to that volume is incredibly slow at 1.8 MB/s and the CPU usage stays near 0%. There are 8 crpyto/1-8 processes running (it's a Intel Quadcore CPU). I hope that someone on serverfault has seen this before :-(. uname -a 2.6.32-5-xen-amd64 #1 SMP Tue Mar 8 00:01:30 UTC 2011 x86_64 GNU/Linux Interestingly, when I read from the device I get good performance numbers: reading without encryption: $ dd if=/dev/vg0/secure of=/dev/null bs=64k count=100000 100000+0 records in 100000+0 records out 6553600000 bytes (6.6 GB) copied, 68.8951 s, 95.1 MB/s reading with encryption: $ dd if=/dev/mapper/secure of=/dev/null bs=64k count=100000 100000+0 records in 100000+0 records out 6553600000 bytes (6.6 GB) copied, 69.7116 s, 94.0 MB/s However, when I try to write to the device: $ dd if=/dev/zero of=./test bs=64k 8809+0 records in 8809+0 records out 577306624 bytes (577 MB) copied, 321.861 s, 1.8 MB/s Also, when I read I see CPU usage, when I write, the CPU stays at almost 0% usage. Here is output of cryptsetup luksDump: LUKS header information for /dev/vg0/secure Version: 1 Cipher name: aes Cipher mode: cbc-essiv:sha256 Hash spec: sha1 Payload offset: 2056 MK bits: 256 MK digest: dd 62 b9 a5 bf 6c ec 23 36 22 92 4c 39 f8 d6 5d c1 3a b7 37 MK salt: cc 2e b3 d9 fb e3 86 a1 bb ab eb 9d 65 df b3 dd d9 6b f4 49 de 8f 85 7d 3b 1c 90 83 5d b2 87 e2 MK iterations: 44500 UUID: a7c9af61-d9f0-4d3f-b422-dddf16250c33 Key Slot 0: ENABLED Iterations: 178282 Salt: 60 24 cb be 5c 51 9f b4 85 64 3d f8 07 22 54 d4 1a 5f 4c bc 4b 82 76 48 d8 a2 d2 6a ee 13 d7 5d Key material offset: 8 AF stripes: 4000 Key Slot 1: DISABLED Key Slot 2: DISABLED Key Slot 3: DISABLED Key Slot 4: DISABLED Key Slot 5: DISABLED Key Slot 6: DISABLED Key Slot 7: DISABLED

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• How to configure VirtualBox server for performance at home

  - by BluJai

  I currently have two physical Ubuntu Server 10.10 servers at home: one serves as our firewall/router/DHCP/VPN server and the other performs double-duty as a file server and a VirtualBox host for an Ubuntu Desktop 10.10 machine which I use from remote connections (via NoMachine) for many thin-client purposes which are irrelevant to my question. What I'd like to accomplish is to consolidate the two physical machines into one which is a dedicated VirtualBox host (most likely running Ubuntu Server 10.10). Note that I'd like to stick with VirtualBox (if possible) because I'm most comfortable with it and use it on a daily basis at both home and work. Specifically, I plan to have one VM set up as file server, another as the firewall/router/DHCP/VPN (or possibly split those a bit) and a third, which is the only current VM (already VirtualBox), which is the thin-client host. My question comes down to performance and/or recommendations about the file server VM. The file server hosts about 6 terabytes of data across 4 drives. What I'd like to do is use raw disk access from the VM directly to the existing disks. However, I'm curious what performance advantage/disadvantage that would have as compared to using shared folders from the VM host and basically just have the whole drive served as a shared folder to the VM which would then serve it to the other machines on the network. I don't know if virtual disks would even work in this scenario and I certainly wouldn't want a drive to be filled with just a single file which is 1.5 TB (disk image). To add understanding of context, but not to get additional advice, I want to virtualize these machines because I intend to regularly use the snapshot capabilities of VirtualBox for the system disks (which will be virtual drives) of the VMs and I have some physical space/power needs to address (as I mentioned, this is at home).

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• How to configure VirtualBox server for performance at home

  - by BluJai

  I currently have two physical Ubuntu Server 10.10 servers at home: one serves as our firewall/router/DHCP/VPN server and the other performs double-duty as a file server and a VirtualBox host for an Ubuntu Desktop 10.10 machine which I use from remote connections (via NoMachine) for many thin-client purposes which are irrelevant to my question. What I'd like to accomplish is to consolidate the two physical machines into one which is a dedicated VirtualBox host (most likely running Ubuntu Server 10.10). Note that I'd like to stick with VirtualBox (if possible) because I'm most comfortable with it and use it on a daily basis at both home and work. Specifically, I plan to have one VM set up as file server, another as the firewall/router/DHCP/VPN (or possibly split those a bit) and a third, which is the only current VM (already VirtualBox), which is the thin-client host. My question comes down to performance and/or recommendations about the file server VM. The file server hosts about 6 terabytes of data across 4 drives. What I'd like to do is use raw disk access from the VM directly to the existing disks. However, I'm curious what performance advantage/disadvantage that would have as compared to using shared folders from the VM host and basically just have the whole drive served as a shared folder to the VM which would then serve it to the other machines on the network. I don't know if virtual disks would even work in this scenario and I certainly wouldn't want a drive to be filled with just a single file which is 1.5 TB (disk image). To add understanding of context, but not to get additional advice, I want to virtualize these machines because I intend to regularly use the snapshot capabilities of VirtualBox for the system disks (which will be virtual drives) of the VMs and I have some physical space/power needs to address (as I mentioned, this is at home).

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• KVM Slow performance on XP Guest

  - by Gregg Leventhal

  The system is very slow to do anything, even browse a local folder, and CPU sits at 100% frequently. Guest is XP 32 bit. Host is Scientific Linux 6.2, Libvirt 0.10, Guest XP OS shows ACPI Multiprocessor HAL and a virtIO driver for NIC and SCSI. Installed. CPUInfo on host: processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 42 model name : Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz stepping : 7 cpu MHz : 3200.000 cache size : 8192 KB physical id : 0 siblings : 8 core id : 0 cpu cores : 4 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid bogomips : 6784.93 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: <memory unit='KiB'>4194304</memory> <currentMemory unit='KiB'>4194304</currentMemory> <vcpu placement='static' cpuset='0'>1</vcpu> <os> <type arch='x86_64' machine='rhel6.3.0'>hvm</type> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <cpu mode='custom' match='exact'> <model fallback='allow'>SandyBridge</model> <vendor>Intel</vendor> <feature policy='require' name='vme'/> <feature policy='require' name='tm2'/> <feature policy='require' name='est'/> <feature policy='require' name='vmx'/> <feature policy='require' name='osxsave'/> <feature policy='require' name='smx'/> <feature policy='require' name='ss'/> <feature policy='require' name='ds'/> <feature policy='require' name='tsc-deadline'/> <feature policy='require' name='dtes64'/> <feature policy='require' name='ht'/> <feature policy='require' name='pbe'/> <feature policy='require' name='tm'/> <feature policy='require' name='pdcm'/> <feature policy='require' name='ds_cpl'/> <feature policy='require' name='xtpr'/> <feature policy='require' name='acpi'/> <feature policy='require' name='monitor'/> <feature policy='force' name='sse'/> <feature policy='force' name='sse2'/> <feature policy='force' name='sse4.1'/> <feature policy='force' name='sse4.2'/> <feature policy='force' name='ssse3'/> <feature policy='force' name='x2apic'/> </cpu> <clock offset='localtime'> <timer name='rtc' tickpolicy='catchup'/> </clock> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/var/lib/libvirt/images/Server-10-9-13.qcow2'/> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/> </disk>

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• EPM 11.1.2 - In WebLogic Server, Enable Native IO Performance Pack

  - by Ahmed Awan

  Performance can be improved by enabling native IO in production mode. WebLogic Server benchmarks show major performance improvements when native performance packs are used on machines that host Oracle WebLogic Server instances. Important Note:  Always enable native I/O, if available, and check for errors at startup to make sure it is being initialed properly. Tip: The use of NATIVE performance packs are enabled by default in the configuration shipped with your distribution. You can use the Administration Console to verify that performance packs are enabled by clicking on each managed server and click on Tuning tab.

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• Adding third disk as a single disk in a server with an existing RAID1

  - by slowhandsolo

  I've got a ProLiant DL360 G5 server (Fedora 13) with two SAS disks in a hardware RAID 1, working fine. Now I hot plugged another SAS disk. I'd like to configure this new hard disk out of my RAID, as a single non-RAID disk (ex. /dev/sdb). Even after rebooting the server, I can't see the new disk with "fdisk -l". It displays only my hardware RAID, but not the new disk. [root@myserver]# fdisk -l Disco /dev/cciss/c0d0: 300.0 GB, 299966445568 bytes Disposit. Inicio Comienzo Fin Bloques Id Sistema /dev/cciss/c0d0p1 * 1 126 512000 83 Linux /dev/cciss/c0d0p2 126 71798 292422656 8e Linux LVM Disco /dev/dm-0: 234.9 GB, 234881024000 bytes Disco /dev/dm-1: 10.5 GB, 10536091648 bytes Disco /dev/dm-2: 21.0 GB, 20971520000 bytes Disco /dev/dm-3: 31.5 GB, 31474057216 bytes Disco /dev/dm-4: 1577 MB, 1577058304 bytes However, I can see the new disk using the HP Array Configuration Utility CLI for Linux "hpacucli": [root@myserver]# hpacucli => controller slot=0 physicaldrive all show status physicaldrive 1I:1:1 (port 1I:box 1:bay 1, 300 GB): OK physicaldrive 1I:1:2 (port 1I:box 1:bay 2, 300 GB): OK physicaldrive 1I:1:3 (port 1I:box 1:bay 3, 300 GB): OK => controller slot=0 pd all show detail Smart Array P400i in Slot 0 (Embedded) array A physicaldrive 1I:1:1 Port: 1I Box: 1 Bay: 1 physicaldrive 1I:1:2 Port: 1I Box: 1 Bay: 2 **unassigned** physicaldrive 1I:1:3 Port: 1I Box: 1 Bay: 3 Status: OK Drive Type: **Unassigned Drive** As you can see, I've got two SAS disks in a RAID 1 and the new disk as "unassigned". Is there any way to work with the new disk as another non-RAID single disk? If relevant, I want to create a new partition in my new disk, format it with mkfs and mount it, but as I can't see it with fdisk, I don't know how to do it. Thanks!

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• How to collect the performance data of a server during an unreachable/down period using Nagios?

  - by gsc-frank

  Some time services and host stop responding due to a poor server performance. I mean, if for some reason (could be lot of concurrency services access, a expensive backup execution on the server or whatever that consume tons of server resources) a server performance is very degraded, that could lead that the server isn't capable to establish any "normal network communication" (without trigger whatever standards timeouts defined for such communication). Knowing host's performance data (cpu, memory, ...) in case of available during that period (host is not down and despite of its performance degradation still allow plugins collect performance data) could be very useful for sysadmin to try to determine what cause the problem, or at least, if the host performance was good and don't interfered at all in the host/service down. This problem could be solved using remote active (NRPE) or remote passive (NSCA) if such remote solutions could store (buffered) perf data to be send to central Nagios server when host performance or network outage allow it. I read the doc of both solutions and can't find any reference to such buffer mechanism neither what happened in case that NSCA can't reach Nagios server. Any idea of how solve this lack of info? so useful for forensic analysis. EDIT: My questions isn about which tools I can use to debug perf problems or gather perf data to analysis, but is about how collect (using Nagios) host perf data even during a network outage for its posterior analysis (kind of forensic analysis). The idea is integrate such data to Nagios graphers like pnp4nagios and NagiosGrapther. I know that I could install tools like Cacti in each of my host, and have a kind of performance data collection redundancy, but I really want avoid that and try to solve all perf analysis requirements with one tools: Nagios

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• Increase application performance on Amazon AWS

  - by Honus Wagner

  I've got a client with an MVC v1 (.NET) application running on a micro instance. On this instance, I've got .NET, IIS 7.5, and MS SQL Server 2008 running to handle the application. The client has reported that it is taking nearly 10 seconds to process each request. Even loading the initial login page takes about that long, then logging in takes that long, etc etc. The currently running instance specs are as follows: 615 MB RAM Intel Xenon CPU E5430 @ 2.66GHz 2.78 GHz 64-Bit Is the memory availability the issue? or is it the processing power? I forsee two options: Change to a larget instance Set up a 2-tier architecture with two micro instances Which of these will give the application better performance? Thanks in advance.

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• Application Performance: The Best of the Web

  - by Michaela Murray

  Wisdom A deep understanding and realization […] resulting in the ability to apply perceptions, judgements and actions. It is also the comprehension of what is true coupled with optimum judgment as to action. - Wikipedia We’re writing a book for ASP.NET developers, and we want you to be a part of it. We know that there’s a huge amount of web developer wisdom that never gets shared, and we want to find those golden nuggets of knowledge and experience, and make sure everyone can learn from them. Right now, we want to find out about your top tips, hard-won lessons, and sage advice for avoiding, finding, and fixing application performance problems. If you work with .NET and SQL, even better – a lot of application performance relies on the interaction with the database, so we want to hear from you! “How Do You Want Me To Be Involved?” Right! Details! We want you, our most excellent readers, to email us with the Best Advice you would give to other developers for getting the best performance out of their applications. It doesn’t matter if your advice is for newbies or veterans, .NET or SQL – so long as it’s about application performance, we want to hear from you. (And if you think that there’s developer wisdom out there that “everyone knows”, a) I’m willing to bet you could find someone who doesn’t know about it, and b) it probably bears repeating anyway!) “I’m Interested. What Can You Do For Me?” Excellent question. For starters, there’s a chance to win a Microsoft Surface (the tablet, not the table-top). Once all the ASP.NET Wisdom has been collected, tallied, and labelled, it will then be weighed and measured by a team of expert judges (whose identities are still a closely-guarded secret).  The top tip in both SQL & .NET categories will each win their author their very own MS Surface. But that’s not all! We can also give you… immortality! More details? Ok. We’ll be collecting all of the tips sent in by our readers (and we can’t wait to learn from you all,) and with the help of our Simple-Talk editors, we will publish and distribute your combined and documented knowledge as a free, community-created, professionally typeset eBook. You will naturally be credited by name / pseudonym / twitter handle / GitHub username / StackOverflow profile / Whatever, as the clearly ingenious author of hot performance tips. The Not-Very-Fine Print Here’s the breakdown: We want to bring together the best application performance knowledge from ASP.NET developers. Closing date for submissions will be 9am GMT, December 4th. Submissions should be made by email – [email protected] Submissions will be judged by a panel of expert judges (who will be revealed soon). The top submission in both the SQL & .NET categories will each win a Microsoft Surface. ALL the tips which make it through the judging process will be polished by Simple-Talk editors, and turned into a professionally typeset eBook, which will be freely available, and promoted alongside the ANTS Performance Profiler tool. Anyone whose entry makes it into the book will be clearly and profusely credited in the method of their choice (or can remain anonymous.) The really REALLY short version Share what you know about ASP.NET application performance for a chance to win a Microsoft Surface, and then get your name credited in a slick eBook with top-notch production values. For more details, see above. We can’t wait to learn from you!

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• Server Performance

  - by sb12

  I know very little about performance tuning of servers etc... so i thought i'd put this up here as i start some research on it, just to get some direction. I am in the process of migrating from my old server to a new one - both are 64 bit machines. One is a few years old, the other brand new (PowerEdge R410). The old server spec is: 2 cpus, 3.4GHz Pentiums, 8G of RAM, Fedora 11 currently installed The new server spec is: 16 cpus, 3.2 GHz Xeon, 16G of RAM, CentOS 6.2 installed. Also RAID10 is on the new server - no RAID on the old one. Both servers currently have the same database (MySQL) with the same data migrated. I wrote a Perl script that simply steps through each row of a table in the database (about 18000 rows) and updates a value in that row. Every row in the table is updated. Out of curiosity i ran this perl script on both machines, just to see how the new server would perform vs. the old one, and it produced interesting results: The old server was twice as fast as the new one to complete. Looking at the database, both are configured exactly the same (the new one being a dump of the old one...)... Anyone any ideas why this would be given the hardware gap between both? As i said i'm about to start some digging, but thought i'd put this up here to maybe get some good direction.... Many thanks in advance..

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• How to mount a blu-ray drive?

  - by Stephan Schielke

  Maybe it is for the best to close this question. This has nothing to do with a bluray drive in general anymore. Probably a hardware defect. I will try to test it with a windows system and different cables again... Thx so far. I have a bluray/dvd/cdrom drive with SATA. Ubuntu wont find it under /dev/sd wodim --devices wodim: Overview of accessible drives (1 found) : ------------------------------------------------------------------------- 0 dev='/dev/sg2' rwrw-- : 'HL-DT-ST' 'BDDVDRW CH08LS10' ------------------------------------------------------------------------- cdrecord -scanbus scsibus2: 2,0,0 200) 'HL-DT-ST' 'BDDVDRW CH08LS10' '2.00' Removable CD-ROM fdisk dont even lists it. Ubuntu only automounts blank DVDs, but neither CDROM nor Blurays. I also changed the sata slot, sata cable and the power cable. The drive works with a windows system. This happens when I try to mount: sudo mount -t auto /dev/scd0 /media/bluray mount: you must specify the filesystem type I tried all filesystems there are. I also installed makemkv. It finds the drive but not the disc. Here is my /dev ls -al /dev total 12 drwxr-xr-x 17 root root 4420 2011-11-25 19:36 . drwxr-xr-x 28 root root 4096 2011-11-25 07:12 .. crw------- 1 root root 10, 235 2011-11-25 19:28 autofs -rw-r--r-- 1 root root 630 2011-11-25 19:28 .blkid.tab -rw-r--r-- 1 root root 630 2011-11-25 19:28 .blkid.tab.old drwxr-xr-x 2 root root 700 2011-11-25 19:27 block drwxr-xr-x 2 root root 100 2011-11-25 19:27 bsg crw------- 1 root root 10, 234 2011-11-25 19:28 btrfs-control drwxr-xr-x 3 root root 60 2011-11-25 19:27 bus drwxr-xr-x 2 root root 3820 2011-11-25 19:28 char crw------- 1 root root 5, 1 2011-11-25 19:28 console lrwxrwxrwx 1 root root 11 2011-11-25 19:28 core -> /proc/kcore drwxr-xr-x 2 root root 60 2011-11-25 19:28 cpu crw------- 1 root root 10, 60 2011-11-25 19:28 cpu_dma_latency drwxr-xr-x 7 root root 140 2011-11-25 19:27 disk crw------- 1 root root 10, 61 2011-11-25 19:28 ecryptfs crw-rw---- 1 root video 29, 0 2011-11-25 19:28 fb0 lrwxrwxrwx 1 root root 13 2011-11-25 19:28 fd -> /proc/self/fd crw-rw-rw- 1 root root 1, 7 2011-11-25 19:28 full crw-rw-rw- 1 root fuse 10, 229 2011-11-25 19:28 fuse crw------- 1 root root 251, 0 2011-11-25 19:28 hidraw0 crw------- 1 root root 251, 1 2011-11-25 19:28 hidraw1 crw------- 1 root root 10, 228 2011-11-25 19:28 hpet lrwxrwxrwx 1 root root 14 2011-11-25 19:27 .initramfs -> /run/initramfs drwxr-xr-x 4 root root 220 2011-11-25 19:28 input crw------- 1 root root 1, 11 2011-11-25 19:28 kmsg srw-rw-rw- 1 root root 0 2011-11-25 19:28 log brw-rw---- 1 root disk 7, 0 2011-11-25 19:28 loop0 brw-rw---- 1 root disk 7, 1 2011-11-25 19:28 loop1 brw-rw---- 1 root disk 7, 2 2011-11-25 19:28 loop2 brw-rw---- 1 root disk 7, 3 2011-11-25 19:28 loop3 brw-rw---- 1 root disk 7, 4 2011-11-25 19:28 loop4 brw-rw---- 1 root disk 7, 5 2011-11-25 19:28 loop5 brw-rw---- 1 root disk 7, 6 2011-11-25 19:28 loop6 brw-rw---- 1 root disk 7, 7 2011-11-25 19:28 loop7 drwxr-xr-x 2 root root 60 2011-11-25 19:27 mapper crw------- 1 root root 10, 227 2011-11-25 19:28 mcelog crw-r----- 1 root kmem 1, 1 2011-11-25 19:28 mem drwxr-xr-x 2 root root 60 2011-11-25 19:27 net crw------- 1 root root 10, 59 2011-11-25 19:28 network_latency crw------- 1 root root 10, 58 2011-11-25 19:28 network_throughput crw-rw-rw- 1 root root 1, 3 2011-11-25 19:28 null crw-rw-rw- 1 root root 195, 0 2011-11-25 19:28 nvidia0 crw-rw-rw- 1 root root 195, 255 2011-11-25 19:28 nvidiactl crw------- 1 root root 1, 12 2011-11-25 19:28 oldmem crw-r----- 1 root kmem 1, 4 2011-11-25 19:28 port crw------- 1 root root 108, 0 2011-11-25 19:28 ppp crw------- 1 root root 10, 1 2011-11-25 19:28 psaux crw-rw-rw- 1 root tty 5, 2 2011-11-25 20:00 ptmx drwxr-xr-x 2 root root 0 2011-11-25 19:27 pts brw-rw---- 1 root disk 1, 0 2011-11-25 19:28 ram0 brw-rw---- 1 root disk 1, 1 2011-11-25 19:28 ram1 brw-rw---- 1 root disk 1, 10 2011-11-25 19:28 ram10 brw-rw---- 1 root disk 1, 11 2011-11-25 19:28 ram11 brw-rw---- 1 root disk 1, 12 2011-11-25 19:28 ram12 brw-rw---- 1 root disk 1, 13 2011-11-25 19:28 ram13 brw-rw---- 1 root disk 1, 14 2011-11-25 19:28 ram14 brw-rw---- 1 root disk 1, 15 2011-11-25 19:28 ram15 brw-rw---- 1 root disk 1, 2 2011-11-25 19:28 ram2 brw-rw---- 1 root disk 1, 3 2011-11-25 19:28 ram3 brw-rw---- 1 root disk 1, 4 2011-11-25 19:28 ram4 brw-rw---- 1 root disk 1, 5 2011-11-25 19:28 ram5 brw-rw---- 1 root disk 1, 6 2011-11-25 19:28 ram6 brw-rw---- 1 root disk 1, 7 2011-11-25 19:28 ram7 brw-rw---- 1 root disk 1, 8 2011-11-25 19:28 ram8 brw-rw---- 1 root disk 1, 9 2011-11-25 19:28 ram9 crw-rw-rw- 1 root root 1, 8 2011-11-25 19:28 random crw-rw-r--+ 1 root root 10, 62 2011-11-25 19:28 rfkill lrwxrwxrwx 1 root root 4 2011-11-25 19:28 rtc -> rtc0 crw------- 1 root root 254, 0 2011-11-25 19:28 rtc0 lrwxrwxrwx 1 root root 3 2011-11-25 19:38 scd0 -> sr0 brw-rw---- 1 root disk 8, 0 2011-11-25 19:28 sda brw-rw---- 1 root disk 8, 1 2011-11-25 19:28 sda1 brw-rw---- 1 root disk 8, 2 2011-11-25 19:28 sda2 brw-rw---- 1 root disk 8, 3 2011-11-25 19:28 sda3 brw-rw---- 1 root disk 8, 5 2011-11-25 19:28 sda5 brw-rw---- 1 root disk 8, 6 2011-11-25 19:28 sda6 brw-rw---- 1 root disk 8, 16 2011-11-25 19:28 sdb brw-rw---- 1 root disk 8, 17 2011-11-25 19:28 sdb1 crw-rw---- 1 root disk 21, 0 2011-11-25 19:28 sg0 crw-rw---- 1 root disk 21, 1 2011-11-25 19:28 sg1 crw-rw----+ 1 root cdrom 21, 2 2011-11-25 19:28 sg2 lrwxrwxrwx 1 root root 8 2011-11-25 19:28 shm -> /run/shm crw------- 1 root root 10, 231 2011-11-25 19:28 snapshot drwxr-xr-x 4 root root 280 2011-11-25 19:28 snd brw-rw----+ 1 root cdrom 11, 0 2011-11-25 19:38 sr0 lrwxrwxrwx 1 root root 15 2011-11-25 19:28 stderr -> /proc/self/fd/2 lrwxrwxrwx 1 root root 15 2011-11-25 19:28 stdin -> /proc/self/fd/0 lrwxrwxrwx 1 root root 15 2011-11-25 19:28 stdout -> /proc/self/fd/1 crw-rw-rw- 1 root tty 5, 0 2011-11-25 19:35 tty crw--w---- 1 root tty 4, 0 2011-11-25 19:28 tty0 crw------- 1 root root 4, 1 2011-11-25 19:28 tty1 crw--w---- 1 root tty 4, 10 2011-11-25 19:28 tty10 crw--w---- 1 root tty 4, 11 2011-11-25 19:28 tty11 crw--w---- 1 root tty 4, 12 2011-11-25 19:28 tty12 crw--w---- 1 root tty 4, 13 2011-11-25 19:28 tty13 crw--w---- 1 root tty 4, 14 2011-11-25 19:28 tty14 crw--w---- 1 root tty 4, 15 2011-11-25 19:28 tty15 crw--w---- 1 root tty 4, 16 2011-11-25 19:28 tty16 crw--w---- 1 root tty 4, 17 2011-11-25 19:28 tty17 crw--w---- 1 root tty 4, 18 2011-11-25 19:28 tty18 crw--w---- 1 root tty 4, 19 2011-11-25 19:28 tty19 crw------- 1 root root 4, 2 2011-11-25 19:28 tty2 crw--w---- 1 root tty 4, 20 2011-11-25 19:28 tty20 crw--w---- 1 root tty 4, 21 2011-11-25 19:28 tty21 crw--w---- 1 root tty 4, 22 2011-11-25 19:28 tty22 crw--w---- 1 root tty 4, 23 2011-11-25 19:28 tty23 crw--w---- 1 root tty 4, 24 2011-11-25 19:28 tty24 crw--w---- 1 root tty 4, 25 2011-11-25 19:28 tty25 crw--w---- 1 root tty 4, 26 2011-11-25 19:28 tty26 crw--w---- 1 root tty 4, 27 2011-11-25 19:28 tty27 crw--w---- 1 root tty 4, 28 2011-11-25 19:28 tty28 crw--w---- 1 root tty 4, 29 2011-11-25 19:28 tty29 crw------- 1 root root 4, 3 2011-11-25 19:28 tty3 crw--w---- 1 root tty 4, 30 2011-11-25 19:28 tty30 crw--w---- 1 root tty 4, 31 2011-11-25 19:28 tty31 crw--w---- 1 root tty 4, 32 2011-11-25 19:28 tty32 crw--w---- 1 root tty 4, 33 2011-11-25 19:28 tty33 crw--w---- 1 root tty 4, 34 2011-11-25 19:28 tty34 crw--w---- 1 root tty 4, 35 2011-11-25 19:28 tty35 crw--w---- 1 root tty 4, 36 2011-11-25 19:28 tty36 crw--w---- 1 root tty 4, 37 2011-11-25 19:28 tty37 crw--w---- 1 root tty 4, 38 2011-11-25 19:28 tty38 crw--w---- 1 root tty 4, 39 2011-11-25 19:28 tty39 crw------- 1 root root 4, 4 2011-11-25 19:28 tty4 crw--w---- 1 root tty 4, 40 2011-11-25 19:28 tty40 crw--w---- 1 root tty 4, 41 2011-11-25 19:28 tty41 crw--w---- 1 root tty 4, 42 2011-11-25 19:28 tty42 crw--w---- 1 root tty 4, 43 2011-11-25 19:28 tty43 crw--w---- 1 root tty 4, 44 2011-11-25 19:28 tty44 crw--w---- 1 root tty 4, 45 2011-11-25 19:28 tty45 crw--w---- 1 root tty 4, 46 2011-11-25 19:28 tty46 crw--w---- 1 root tty 4, 47 2011-11-25 19:28 tty47 crw--w---- 1 root tty 4, 48 2011-11-25 19:28 tty48 crw--w---- 1 root tty 4, 49 2011-11-25 19:28 tty49 crw------- 1 root root 4, 5 2011-11-25 19:28 tty5 crw--w---- 1 root tty 4, 50 2011-11-25 19:28 tty50 crw--w---- 1 root tty 4, 51 2011-11-25 19:28 tty51 crw--w---- 1 root tty 4, 52 2011-11-25 19:28 tty52 crw--w---- 1 root tty 4, 53 2011-11-25 19:28 tty53 crw--w---- 1 root tty 4, 54 2011-11-25 19:28 tty54 crw--w---- 1 root tty 4, 55 2011-11-25 19:28 tty55 crw--w---- 1 root tty 4, 56 2011-11-25 19:28 tty56 crw--w---- 1 root tty 4, 57 2011-11-25 19:28 tty57 crw--w---- 1 root tty 4, 58 2011-11-25 19:28 tty58 crw--w---- 1 root tty 4, 59 2011-11-25 19:28 tty59 crw------- 1 root root 4, 6 2011-11-25 19:28 tty6 crw--w---- 1 root tty 4, 60 2011-11-25 19:28 tty60 crw--w---- 1 root tty 4, 61 2011-11-25 19:28 tty61 crw--w---- 1 root tty 4, 62 2011-11-25 19:28 tty62 crw--w---- 1 root tty 4, 63 2011-11-25 19:28 tty63 crw--w---- 1 root tty 4, 7 2011-11-25 19:28 tty7 crw--w---- 1 root tty 4, 8 2011-11-25 19:28 tty8 crw--w---- 1 root tty 4, 9 2011-11-25 19:28 tty9 crw------- 1 root root 5, 3 2011-11-25 19:28 ttyprintk crw-rw---- 1 root dialout 4, 64 2011-11-25 19:28 ttyS0 crw-rw---- 1 root dialout 4, 65 2011-11-25 19:28 ttyS1 crw-rw---- 1 root dialout 4, 74 2011-11-25 19:28 ttyS10 crw-rw---- 1 root dialout 4, 75 2011-11-25 19:28 ttyS11 crw-rw---- 1 root dialout 4, 76 2011-11-25 19:28 ttyS12 crw-rw---- 1 root dialout 4, 77 2011-11-25 19:28 ttyS13 crw-rw---- 1 root dialout 4, 78 2011-11-25 19:28 ttyS14 crw-rw---- 1 root dialout 4, 79 2011-11-25 19:28 ttyS15 crw-rw---- 1 root dialout 4, 80 2011-11-25 19:28 ttyS16 crw-rw---- 1 root dialout 4, 81 2011-11-25 19:28 ttyS17 crw-rw---- 1 root dialout 4, 82 2011-11-25 19:28 ttyS18 crw-rw---- 1 root dialout 4, 83 2011-11-25 19:28 ttyS19 crw-rw---- 1 root dialout 4, 66 2011-11-25 19:28 ttyS2 crw-rw---- 1 root dialout 4, 84 2011-11-25 19:28 ttyS20 crw-rw---- 1 root dialout 4, 85 2011-11-25 19:28 ttyS21 crw-rw---- 1 root dialout 4, 86 2011-11-25 19:28 ttyS22 crw-rw---- 1 root dialout 4, 87 2011-11-25 19:28 ttyS23 crw-rw---- 1 root dialout 4, 88 2011-11-25 19:28 ttyS24 crw-rw---- 1 root dialout 4, 89 2011-11-25 19:28 ttyS25 crw-rw---- 1 root dialout 4, 90 2011-11-25 19:28 ttyS26 crw-rw---- 1 root dialout 4, 91 2011-11-25 19:28 ttyS27 crw-rw---- 1 root dialout 4, 92 2011-11-25 19:28 ttyS28 crw-rw---- 1 root dialout 4, 93 2011-11-25 19:28 ttyS29 crw-rw---- 1 root dialout 4, 67 2011-11-25 19:28 ttyS3 crw-rw---- 1 root dialout 4, 94 2011-11-25 19:28 ttyS30 crw-rw---- 1 root dialout 4, 95 2011-11-25 19:28 ttyS31 crw-rw---- 1 root dialout 4, 68 2011-11-25 19:28 ttyS4 crw-rw---- 1 root dialout 4, 69 2011-11-25 19:28 ttyS5 crw-rw---- 1 root dialout 4, 70 2011-11-25 19:28 ttyS6 crw-rw---- 1 root dialout 4, 71 2011-11-25 19:28 ttyS7 crw-rw---- 1 root dialout 4, 72 2011-11-25 19:28 ttyS8 crw-rw---- 1 root dialout 4, 73 2011-11-25 19:28 ttyS9 d rwxr-xr-x 3 root root 60 2011-11-25 19:28 .udev crw-r----- 1 root root 10, 223 2011-11-25 19:28 uinput crw-rw-rw- 1 root root 1, 9 2011-11-25 19:28 urandom drwxr-xr-x 2 root root 60 2011-11-25 19:27 usb crw------- 1 root root 252, 0 2011-11-25 19:28 usbmon0 crw------- 1 root root 252, 1 2011-11-25 19:28 usbmon1 crw------- 1 root root 252, 2 2011-11-25 19:28 usbmon2 crw------- 1 root root 252, 3 2011-11-25 19:28 usbmon3 crw------- 1 root root 252, 4 2011-11-25 19:28 usbmon4 crw------- 1 root root 252, 5 2011-11-25 19:28 usbmon5 crw------- 1 root root 252, 6 2011-11-25 19:28 usbmon6 crw------- 1 root root 252, 7 2011-11-25 19:28 usbmon7 crw------- 1 root root 252, 8 2011-11-25 19:28 usbmon8 drwxr-xr-x 4 root root 80 2011-11-25 19:28 v4l crw------- 1 root root 10, 57 2011-11-25 19:28 vboxdrv crw------- 1 root root 10, 56 2011-11-25 19:28 vboxnetctl drwxr-x--- 4 root vboxusers 80 2011-11-25 19:28 vboxusb crw-rw---- 1 root tty 7, 0 2011-11-25 19:28 vcs crw-rw---- 1 root tty 7, 1 2011-11-25 19:28 vcs1 crw-rw---- 1 root tty 7, 2 2011-11-25 19:28 vcs2 crw-rw---- 1 root tty 7, 3 2011-11-25 19:28 vcs3 crw-rw---- 1 root tty 7, 4 2011-11-25 19:28 vcs4 crw-rw---- 1 root tty 7, 5 2011-11-25 19:28 vcs5 crw-rw---- 1 root tty 7, 6 2011-11-25 19:28 vcs6 crw-rw---- 1 root tty 7, 128 2011-11-25 19:28 vcsa crw-rw---- 1 root tty 7, 129 2011-11-25 19:28 vcsa1 crw-rw---- 1 root tty 7, 130 2011-11-25 19:28 vcsa2 crw-rw---- 1 root tty 7, 131 2011-11-25 19:28 vcsa3 crw-rw---- 1 root tty 7, 132 2011-11-25 19:28 vcsa4 crw-rw---- 1 root tty 7, 133 2011-11-25 19:28 vcsa5 crw-rw---- 1 root tty 7, 134 2011-11-25 19:28 vcsa6 crw------- 1 root root 10, 63 2011-11-25 19:28 vga_arbiter crw-rw----+ 1 root video 81, 0 2011-11-25 19:28 video0 crw-rw-rw- 1 root root 1, 5 2011-11-25 19:28 zero sg_scan -i gives me: sudo sg_scan -i /dev/sg0: scsi0 channel=0 id=0 lun=0 [em] ATA ST31000524NS SN12 [rmb=0 cmdq=0 pqual=0 pdev=0x0] /dev/sg1: scsi0 channel=0 id=1 lun=0 [em] ATA WDC WD15EADS-00S 01.0 [rmb=0 cmdq=0 pqual=0 pdev=0x0] /dev/sg2: scsi2 channel=0 id=0 lun=0 [em] HL-DT-ST BDDVDRW CH08LS10 2.00 [rmb=1 cmdq=0 pqual=0 pdev=0x5] sg_map gives me: /dev/sg0 /dev/sda /dev/sg1 /dev/sdb /dev/sg2 /dev/scd0 lsscsi -l gives me: [0:0:0:0] disk ATA ST31000524NS SN12 /dev/sda state=running queue_depth=1 scsi_level=6 type=0 device_blocked=0 timeout=30 [0:0:1:0] disk ATA WDC WD15EADS-00S 01.0 /dev/sdb state=running queue_depth=1 scsi_level=6 type=0 device_blocked=0 timeout=30 [2:0:0:0] cd/dvd HL-DT-ST BDDVDRW CH08LS10 2.00 /dev/sr0 state=running queue_depth=1 scsi_level=6 type=5 device_blocked=0 timeout=30 my udf mod is: filename: /lib/modules/3.0.0-14-generic/kernel/fs/udf/udf.ko license: GPL description: Universal Disk Format Filesystem author: Ben Fennema srcversion: 6ABDE012374D96B9685B8E5 depends: crc-itu-t vermagic: 3.0.0-14-generic SMP mod_unload modversions Do I need special drivers or mods enabled? Do I need to change some BIOS settings? edit: Somehow I am now able to fire the mount command without any filesystem errors, but now I get: mount: no medium found on /dev/sr0

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• Analysing and measuring the performance of a .NET application (survey results)

  - by Laila

  Back in December last year, I asked myself: could it be that .NET developers think that you need three days and a PhD to do performance profiling on their code? What if developers are shunning profilers because they perceive them as too complex to use? If so, then what method do they use to measure and analyse the performance of their .NET applications? Do they even care about performance? So, a few weeks ago, I decided to get a 1-minute survey up and running in the hopes that some good, hard data would clear the matter up once and for all. I posted the survey on Simple Talk and got help from a few people to promote it. The survey consisted of 3 simple questions: Amazingly, 533 developers took the time to respond - which means I had enough data to get representative results! So before I go any further, I would like to thank all of you who contributed, because I now have some pretty good answers to the troubling questions I was asking myself. To thank you properly, I thought I would share some of the results with you. First of all, application performance is indeed important to most of you. In fact, performance is an intrinsic part of the development cycle for a good 40% of you, which is much higher than I had anticipated, I have to admit. (I know, "Have a little faith Laila!") When asked what tool you use to measure and analyse application performance, I found that nearly half of the respondents use logging statements, a third use performance counters, and 70% of respondents use a profiler of some sort (a 3rd party performance profilers, the CLR profiler or the Visual Studio profiler). The importance attributed to logging statements did surprise me a little. I am still not sure why somebody would go to the trouble of manually instrumenting code in order to measure its performance, instead of just using a profiler. I personally find the process of annotating code, calculating times from log files, and relating it all back to your source terrifyingly laborious. Not to mention that you then need to remember to turn it all off later! Even when you have logging in place throughout all your code anyway, you still have a fair amount of potentially error-prone calculation to sift through the results; in addition, you'll only get method-level rather than line-level timings, and you won't get timings from any framework or library methods you don't have source for. To top it all, we all know that bottlenecks are rarely where you would expect them to be, so you could be wasting time looking for a performance problem in the wrong place. On the other hand, profilers do all the work for you: they automatically collect the CPU and wall-clock timings, and present the results from method timing all the way down to individual lines of code. Maybe I'm missing a trick. I would love to know about the types of scenarios where you actively prefer to use logging statements. Finally, while a third of the respondents didn't have a strong opinion about code performance profilers, those who had an opinion thought that they were mainly complex to use and time consuming. Three respondents in particular summarised this perfectly: "sometimes, they are rather complex to use, adding an additional time-sink to the process of trying to resolve the existing problem". "they are simple to use, but the results are hard to understand" "Complex to find the more advanced things, easy to find some low hanging fruit". These results confirmed my suspicions: Profilers are seen to be designed for more advanced users who can use them effectively and make sense of the results. I found yet more interesting information when I started comparing samples of "developers for whom performance is an important part of the dev cycle", with those "to whom performance is only looked at in times of crisis", and "developers to whom performance is not important, as long as the app works". See the three graphs below. Sample of developers to whom performance is an important part of the dev cycle: Sample of developers to whom performance is important only in times of crisis: Sample of developers to whom performance is not important, as long as the app works: As you can see, there is a strong correlation between the usage of a profiler and the importance attributed to performance: indeed, the more important performance is to a development team, the more likely they are to use a profiler. In addition, developers to whom performance is an important part of the dev cycle have a higher tendency to use a much wider range of methods for performance measurement and analysis. And, unsurprisingly, the less important performance is, the less varied the methods of measurement are. So all in all, to come back to my random questions: .NET developers do care about performance. Those who care the most use a wider range of performance measurement methods than those who care less. But overall, logging statements, performance counters and third party performance profilers are the performance measurement methods of choice for most developers. Finally, although most of you find code profilers complex to use, those of you who care the most about performance tend to use profilers more than those of you to whom performance is not so important.

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• rsync'd a folder, folder doesn't show up, but free disk space decreased

  - by Patrick

  I am currently trying to switch from mac to windows/ubuntu dual boot (on 2 seperate internal HDDs), but ran into some trouble restoring my documents. I am not sure all the information below is necessary, but if I knew how to solve it, I wouldn't ask it here. I backed up my mac before buying this laptop on an external HDD with Carbon Copy Cloner. I wanted to put these files on my user folder on my windows HDD, but I could not do that from inside windows (HFS+ format of mac), so I used rsync from inside Ubuntu to copy the documents from the ext hdd to the windows partition. It seemed like it went okay, but from inside windows (and later also Ubuntu) the folder didn't show up. My free HDD space, however, has reduced with about 200 GB (the size of the backup) when looking at the disk properties (from inside Windows and Ubuntu). rsync command I used: rsync -av /media/patrick/Toshiba\ 1.5T/Users/patrickvandenberg/ /media/patrick/Windows8_OS/Users/Patrick/MacBackup/ Folder does not exist: patrick@patrick-Lenovo-IdeaPad-Y410P:~$ cd /media/patrick/Windows8_OS/Users/Patrick/MacBackup bash: cd: /media/patrick/Windows8_OS/Users/Patrick/MacBackup: No such file or directory Size of disk: patrick@patrick-Lenovo-IdeaPad-Y410P:~$ du -hs /media/patrick/Windows8_OS/ 195G /media/patrick/Windows8_OS/ Size of disk according to Disk properties: http://i.stack.imgur.com/OteMX.png (not enough rep to insert the image)

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• Why is my disk full?

  - by Agmenor

  I installed Ubuntu 12.04 by doing a fresh install where there was previously Ubuntu 11.10. My computer warns me now that my disk is nearly full. After having run apt-get purge, run apt-get autoremove and emptied the Trash can, I still have this problem as shown by this screenshot of Gparted: The disk /dev/sda7 is indeed full. I ran the Disk Usage Analyzer (Baobab) and I am still not sure of what is happening: One of my hypothesis is that when installing Ubuntu 12.04, I didn't configure my disks well and the disk /dev/sda6 is not mounted well as /home. Is this the reason indeed? What should I do to verify this and then to get the things fixed? Here are a few additional details to answer the questions I received (thank you everybody): My home directory is not encrypted. The Backup utility (Déjà Dup) is not set for automatic backups. (I do it myself and manually.) After I mount /dev/sda6, the command df -h gives Filesystem Size Used Avail Use% Mounted on /dev/sda7 244G 221G 12G 96% / udev 3,9G 4,0K 3,9G 1% /dev tmpfs 1,6G 904K 1,6G 1% /run none 5,0M 0 5,0M 0% /run/lock none 3,9G 164K 3,9G 1% /run/shm /dev/sda6 653G 189G 433G 31% /media/8ec2fa69-039b-4c52-ab1b-034d785132a1 (sorry but formatting this into code does not work, for an unknown reason) Thanks to izx's post, I realized /dev/sda6 was not even mounted before. It contains all the documents I used to have when I was running Ubuntu 11.10.

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• C# Performance Pitfall – Interop Scenarios Change the Rules

  - by Reed

  C# and .NET, overall, really do have fantastic performance in my opinion.  That being said, the performance characteristics dramatically differ from native programming, and take some relearning if you’re used to doing performance optimization in most other languages, especially C, C++, and similar.  However, there are times when revisiting tricks learned in native code play a critical role in performance optimization in C#. I recently ran across a nasty scenario that illustrated to me how dangerous following any fixed rules for optimization can be… The rules in C# when optimizing code are very different than C or C++.  Often, they’re exactly backwards.  For example, in C and C++, lifting a variable out of loops in order to avoid memory allocations often can have huge advantages.  If some function within a call graph is allocating memory dynamically, and that gets called in a loop, it can dramatically slow down a routine. This can be a tricky bottleneck to track down, even with a profiler.  Looking at the memory allocation graph is usually the key for spotting this routine, as it’s often “hidden” deep in call graph.  For example, while optimizing some of my scientific routines, I ran into a situation where I had a loop similar to: for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i]); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This loop was at a fairly high level in the call graph, and often could take many hours to complete, depending on the input data.  As such, any performance optimization we could achieve would be greatly appreciated by our users. After a fair bit of profiling, I noticed that a couple of function calls down the call graph (inside of ProcessElement), there was some code that effectively was doing: // Allocate some data required DataStructure* data = new DataStructure(num); // Call into a subroutine that passed around and manipulated this data highly CallSubroutine(data); // Read and use some values from here double values = data->Foo; // Cleanup delete data; // ... return bar; Normally, if “DataStructure” was a simple data type, I could just allocate it on the stack.  However, it’s constructor, internally, allocated it’s own memory using new, so this wouldn’t eliminate the problem.  In this case, however, I could change the call signatures to allow the pointer to the data structure to be passed into ProcessElement and through the call graph, allowing the inner routine to reuse the same “data” memory instead of allocating.  At the highest level, my code effectively changed to something like: DataStructure* data = new DataStructure(numberToProcess); for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i], data); } delete data; Granted, this dramatically reduced the maintainability of the code, so it wasn’t something I wanted to do unless there was a significant benefit.  In this case, after profiling the new version, I found that it increased the overall performance dramatically – my main test case went from 35 minutes runtime down to 21 minutes.  This was such a significant improvement, I felt it was worth the reduction in maintainability. In C and C++, it’s generally a good idea (for performance) to: Reduce the number of memory allocations as much as possible, Use fewer, larger memory allocations instead of many smaller ones, and Allocate as high up the call stack as possible, and reuse memory I’ve seen many people try to make similar optimizations in C# code.  For good or bad, this is typically not a good idea.  The garbage collector in .NET completely changes the rules here. In C#, reallocating memory in a loop is not always a bad idea.  In this scenario, for example, I may have been much better off leaving the original code alone.  The reason for this is the garbage collector.  The GC in .NET is incredibly effective, and leaving the allocation deep inside the call stack has some huge advantages.  First and foremost, it tends to make the code more maintainable – passing around object references tends to couple the methods together more than necessary, and overall increase the complexity of the code.  This is something that should be avoided unless there is a significant reason.  Second, (unlike C and C++) memory allocation of a single object in C# is normally cheap and fast.  Finally, and most critically, there is a large advantage to having short lived objects.  If you lift a variable out of the loop and reuse the memory, its much more likely that object will get promoted to Gen1 (or worse, Gen2).  This can cause expensive compaction operations to be required, and also lead to (at least temporary) memory fragmentation as well as more costly collections later. As such, I’ve found that it’s often (though not always) faster to leave memory allocations where you’d naturally place them – deep inside of the call graph, inside of the loops.  This causes the objects to stay very short lived, which in turn increases the efficiency of the garbage collector, and can dramatically improve the overall performance of the routine as a whole. In C#, I tend to: Keep variable declarations in the tightest scope possible Declare and allocate objects at usage While this tends to cause some of the same goals (reducing unnecessary allocations, etc), the goal here is a bit different – it’s about keeping the objects rooted for as little time as possible in order to (attempt) to keep them completely in Gen0, or worst case, Gen1.  It also has the huge advantage of keeping the code very maintainable – objects are used and “released” as soon as possible, which keeps the code very clean.  It does, however, often have the side effect of causing more allocations to occur, but keeping the objects rooted for a much shorter time. Now – nowhere here am I suggesting that these rules are hard, fast rules that are always true.  That being said, my time spent optimizing over the years encourages me to naturally write code that follows the above guidelines, then profile and adjust as necessary.  In my current project, however, I ran across one of those nasty little pitfalls that’s something to keep in mind – interop changes the rules. In this case, I was dealing with an API that, internally, used some COM objects.  In this case, these COM objects were leading to native allocations (most likely C++) occurring in a loop deep in my call graph.  Even though I was writing nice, clean managed code, the normal managed code rules for performance no longer apply.  After profiling to find the bottleneck in my code, I realized that my inner loop, a innocuous looking block of C# code, was effectively causing a set of native memory allocations in every iteration.  This required going back to a “native programming” mindset for optimization.  Lifting these variables and reusing them took a 1:10 routine down to 0:20 – again, a very worthwhile improvement. Overall, the lessons here are: Always profile if you suspect a performance problem – don’t assume any rule is correct, or any code is efficient just because it looks like it should be Remember to check memory allocations when profiling, not just CPU cycles Interop scenarios often cause managed code to act very differently than “normal” managed code. Native code can be hidden very cleverly inside of managed wrappers

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• How to save a perfmon Performance Counter as a textfile (Reliability and Performance Monitor Version

  - by Lieven Cardoen

  Now the file gets saved as blg, but I would like a txt versin to import in Excel.

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• Low disk space: home/user folder occupies 94GB

  - by tedtoy

  I am low on disk space and when I check the Disk Usage analyzer (using gksudo baobab) it indicates that my home/teddy folder is using 94GB, but when I browse through its contents I can only account for about 1gb of that usage. I've tried sudo apt-get clean and deleting the cached package files from Synaptic Package Manager, emptied trash but that has not changed the amount of free space I have. It seems similar to this problem But using the root disk usage analyzer has not given any insight into what is consuming so much space. Any ideas?

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• How often is software speed evident in the eyes of customers?

  - by rwong

  In theory, customers should be able to feel the software performance improvements from first-hand experience. In practice, sometimes the improvements are not noticible enough, such that in order to monetize from the improvements, it is necessary to use quotable performance figures in marketing in order to attract customers. We already know the difference between perceived performance (GUI latency, etc) and server-side performance (machines, networks, infrastructure, etc). How often is it that programmers need to go the extra length to "write up" performance analyses for which the audience is not fellow programmers, but managers and customers?

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• Command line method to find disk usage of camera mounted using gvfs

  - by Hamish Downer

  When my camera was mounted on /media I could use the standard tools (df) to see the disk usage of the card in my camera. However now the camera is mounted using gvfs, and df seems to ignore it. I've also tried pydf and discus to no avail. The camera is definitely available through nautilus, and when I select the camera in nautlius, the status bar tells me the amount of disk free. I can also open the ~/.gvfs/ folder in nautilus and right click on the camera folder and get the disk usage in a graphical way. But that is no use for a script. Are there command line tools that are the equivalent of df for gvfs filesystems? Or even better, a way to make df report on gvfs filesystems?

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• After Installation Whole Disk Encryption? 12.04

  - by Luke

  I know some fragments of this question have been asked in previous posts and I have reviewed them - however I have a more thorough question... I did not choose to do whole disk encryption when I used the alternative installer to install my 12.04 distro. I thought that truecypt worked with linux on system drive (whole disk) encryption - but sadly found out it did not. I have totally tweaked and pimped out my installation and I do not want to have to go back and "install" to just get whole disk encryption. Any alternatives that anyone knows of? I don't want just /home... I want the whole system installation protected and made secure so that when I boot I get a password to unencrypt.

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