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• smartOS HPC config suggestion

  - by Andrew B.

  I'm configuring a brand new HPC server and am interested in using SmartOS because of it's virtualization control and zfs features. Does this configuration make sense for a SmartOS HPC, or would you recommend an alternative? System Specs: 2x 8-core xeon 384 GB RAM 30 TB HDs with 2x512GB SSDs Uses: - zfs for serving data to different vms, and over the network; 1 SSD for L2ARC and 1 for ZIL - typically 1-2 ubuntu instances running R and custom C/C++ code My biggest concerns as a newbie to SmartOS and ZFS are: (1) will I get near-metal performance from ubuntu running on SmartOS if it is the only active vm? (2) how do I serve data from the global zfs pool to the containers and other network devices?

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• What's faster for web-server virtualization ? (virtualbox or KVM)

  - by marc

  I have question, does anyone try to set up a webserver (debian) using virtualbox (x64) ? Right now i have few servers in KVM (x64) but i think it work slowly... Can i get something more (faster, performance) using virtualbox (x64)? On my home installation it looks very fast. Should i move to vbox against kvm ? I'm looking for answer from someone who have in virtualbox (x64) real server (can be headless) (debian/ubuntu) not windows xp or other home using things ;) I also got xp, 2k3, ubuntu in virtualbox (x86) and for me looking faster than kvm(x64). But it's hard to say anything without real tests done by multiple users not just one.

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• How do you handle the task of changing the schema of a production MySQL database?

  - by Continuation

  One of the biggest complaints I have heard about MySQL is that it locks up a table if you try to change its schema like adding a column or adding an index. By "locking up the table" does it mean I can neither read nor write to the table? Sometimes for hours? That seems a pretty severe limitations. I was going to use MySQL for my new project but this gives me pause. Is there a workaround for this? How do you handle the task of changing the schema of your production MySQL database? By the way someone told me Postgresql doesn't have this problem. Is that true - I can both read and write to a Postgresql table while changing its schema? Is there any performance penalty incurred? Would love to hear your experiences.

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• Graphic Setup tune-up checklist

  - by Click Ok

  I was trying to play the game Warzone 2100 and the games runs fine, with nice speed, but the screen stays with a horizontal lines "flickering"... My PC have a integrated GeForce Go 6100 vga. Ok, not a powerfull vga, but it's not the end of the world to run a "simple" game like this (compared with another games that ask you send your eyes to purchase a expensive vga). So, I think that the problem can be of the configuration of my machine. I use it in first instance for programming jobs, so I underpay attention to video setup. I would like about a checklist to know if my PC is "ready" to games. By example, I know that I need: Lastest vga drivers Updated DirectX and OpenGL What you suggest? There is too some good programs to test performance and suggests improvements in the system? Thank you! PS: I'm using Windows 7

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• Linux IO scheduler on databases with RAID

  - by Raghu

  Hi, I have a linux database(MySQL) server(Dell 2950) with a 6-disk RAID 10. The default IO scheduler on it is CFQ. However, from what I have read and heard, there is no need for a scheduler like CFQ when reordering/scheduling is also done by underlying RAID controller; on the contrary since it does not account underlying RAID configuration into account performance may actually degrade with CFQ. The primary concern is to reduce CPU usage and improve throughput. Also, I have seen recommendations of using noop/deadline IO scheduler for databases primarily because of the nature of their R/W access.

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• Upgrade no raid server to raid

  - by AZee

  I have just learned that our PDC has a single drive with 2 partitions. I also know that this drive has bad blocks as recorded in the event log. What I would like to do is to convert this to a RAID solution with a nice balance between economy and performance. I will admit that I have only configured servers with RAID from scratch, and have no experience upgrading an existing system into a RAID system. In fact, I'm not sure it is even possible. Since this is the PDC for 350+ workstations downtime is important. I'd like to hear from other System Administators how they would tackle this and their recommendations for all devices. At this time it seems to me that I can replace the existing drive and then restore from backup or install a controller, drives, configure the RAID an basically start from scratch. Thank you for taking your time. ~AZee

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• Virtualbox, merging snapshots and base disk

  - by Henrik

  Hi, I have a virtual machine with about 30 snapshots in branches. The current development path is 22 snapshots plus the base disk. The amount of files is seemingly having an impact now on IO and the dev laptop I'm using (don't know if it is host disk performance issues with the 140GB total size over a lot of fragments, or just the fact that it is hitting sectors distributed across a lot of files). I would like to merge the current development branch of snapshots together with the base disk, but I am unsure if the following command would produce the correct outcome. I am not able to boot this disk after the procedure completes (5-6 hours). vboxmanage clonehd "C:\VPC-Storage\.VirtualBox\Machines\CRM\Snapshots\{245b27ac-e658-470a-b978-8e62137c33b1}.vhd" "E:\crm-20100624.vhd" --format VHD --type normal Could anyone confirm if this is the correct approach or not?

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• Sudden slow read & write speed on all IO

  - by user23392

  I have a custom built rig that has 2 storage drives. for OS: Western Digital 1.0TB HARD DR 64MB for other stuff: Corsair Performance 3 128GB (SSD) [ expected read speed: 400 mb/s ] The system was incredibly fast for a couple of months, then one day i was playing a game then it started to get buggy (some sounds and objects disappearing), i stopped the game and the system seemed to be unstable so i had to shut it down, next morning i couldn't start it up, it was saying something about corrupt device. I formatted both disks and installed a fresh copy of windows, all i can say that since that day the system was never like before, it takes 10 minutes to boot up (the icons and desktop slowly appear). but once it's done the slowness isn't as noticeable. Here's my benchmark on the HDD ( read speed - write speed ): And the SSD: Anyone knows what could be the issue?

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• How to find malicious IPs?

  - by alfish

  Cacti shows irregular and pretty steady high bandwidth to my server (40x the normal) so I guess the server is udnder some sort of DDoS attack. The incoming bandwidth has not paralyzed my server, but of course consuming the bandwidth and affects performance so I am keen to figure out the possible culprits IPs add them to my deny list or otherwise counter them. When I run: netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n I get a long list of IPs with up to 400 connections each. I checked the most numerous occurring IPs but they come from my CDN. So I am wondering what is the best way to help monitor the requests that each IP make in order to pinpoint the malicious ones. I am using Ubuntu server. Thanks

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• slow disk writes between host and guest

  - by Jure1873

  I've got a ubuntu (server kernel) on a amd x4, 4gb ram, 2x seagate sata 1 tb disks for testing virtual machines and the write performance is very slow. The two disks are in a software raid1 array, one small boot ext3 partition, 10gb system partition and the rest is a xfs partition (about 980) gb for data (virtual machines). If I'm copying files from the virtual machine to the host with rsync or scp the copy frequently stalls or goes at about 1mb/s. What's wrong? I've tried disabling barriers on xfs, increased logbufs, allocsize, but it seems nothing helps. The strange thing is that await (for example during copying) for sda is usually under 100, while for sdb is around 400. Any ideas on what could be wrong / what could I do to improve this setup?

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• Mitigating the 'firesheep' attack at the network layer?

  - by pobk

  What are the sysadmin's thoughts on mitigating the 'firesheep' attack for servers they manage? Firesheep is a new firefox extension that allows anyone who installs it to sidejack session it can discover. It does it's discovery by sniffing packets on the network and looking for session cookies from known sites. It is relatively easy to write plugins for the extension to listen for cookies from additional sites. From a systems/network perspective, we've discussed the possibility of encrypting the whole site, but this introduces additional load on servers and screws with site-indexing, assets and general performance. One option we've investigated is to use our firewalls to do SSL Offload, but as I mentioned earlier, this would require all of the site to be encrypted. What's the general thoughts on protecting against this attack vector? I've asked a similar question on StackOverflow, however, it would be interesting to see what the systems engineers thought.

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• Pages partially load on rapid refresh

  - by user101570

  I recently set up a VPS slice with 256MB to run a LAMP stack (Ubuntu 11.04, Apache2, Mysql, PHP5). So far I'm only running a simple Wordpress site on an IP-based virtual host I set up. The performance is excellent, but I've noticed that if I send multiple HTTP requests from the same IP in a short time period, only partial pages are rendered. Then if I wait a bit and refresh the page, the entire page loads again. I noticed this behaviour when accessing the site from two browsers from my office desktop, but it also presents itself if I quickly navigate the site from a single browser (any browser). I'm guessing this is an Apache phenomenon, as the pages are rendered correctly except under the conditions above, but perhaps I'm wrong here. Could it be my hosting company with some kind of DOS protection in place? As a relative Linux/server noob, I'd really appreciate any insight into what settings in Apache could explain this behaviour, and how I might go about changing it.

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• BES 5.0 and MAPI calls to exchange system

  - by nysingh

  We have been using BES 4.1(5) for a while now and it has been a resource hog on exchange due to high number of MAPI calls. I have heard that BES 5.0 is even worse. the comparison i heard is that BES 4.1 is makes MAPI calls equal to 5 outlook clients per BB user and BES 5.0 makes MAPI calls equal to 10 outlook clients per BB user. can someone confirm if it is true? is BES 5.0 is really that bad in MAPI calls and for exchange performance. ? thanks

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• Will SSD degrade when running VMWare Workstation from SSD?

  - by Andrey Botalov

  My main OS (Windows 7 or 8) is runned from SSD. I'd want to run Mac OS X 10.7 or 10.8 using VMWare workstation. I've heard that VMWare doesn't support TRIM and other things to optimize SSD usage. So SSD will quickly degrade if VM will be runned from SSD. Will it be better to put guest OS's files (.vmdk and the rest) to external HDD (connected through USB 2 or 3) instead of SSD? What advantages and disadvantages it will give? What if VM will be put to internal HDD? At what drive type performance of VM will be better?

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• Improve efficiency when using parallel to read from compressed stream

  - by Yoga

  Is another question extended from the previous one [1] I have a compressed file and stream them to feed into a python program, e.g. bzcat data.bz2 | parallel --no-notice -j16 --pipe python parse.py > result.txt The parse.py can read from stdin continusuoly and print to stdout My ec2 instance is 16 cores but from the top command it is showing 3 to 4 load average only. From the ps, I am seeing a lot of stuffs like.. sh -c 'dd bs=1 count=1 of=/tmp/7D_YxccfY7.chr 2>/dev/null'; I know I can improve using the -a in.txtto improve performance, but with my case I am streaming from bz2 (I cannot exact it since I don't have enought disk space) How to improve the efficiency for my case? [1] Gnu parallel not utilizing all the CPU

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• Evaluate a vendor laptop before deployment to user?

  - by NetWarrior

  I get numerous requests from executives and users for new smaller laptops for travel purposes. Most of my evaluation is based upon whether or not it can run certain applications. Mainly lotus notes, office, and video. Most of the laptops include windows 7 OS, and are fully loaded with ram, a high-end processor and a integrated graphics card. My boss whats me to document the usefulness of the laptop and performance. I'm just a little confused on how to setup a document that can be used by members of the IT department for future evaluations.

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• Windows 8 / Server 2012 RDP connection is slow

  - by Chris

  I recently installed Windows Server 2012 for development purposes at our office and noticed immediately that connecting via RDP is slow. It can take 5-10 seconds to connect at times, where as connecting to any of our Win7 or Win2008R2 boxes takes at most 1-3 seconds. At first, I chalked this up to the box itself needing a driver update or something, but just yesterday, I installed Win8 on my desk PC and connecting from home to that machine produces the same result. There is a 3-4 second pause at "securing remote connection" and then again at "configuring remote session". I don't see any warnings in the event log, and once connected, there do not appear to be any performance issues. Is there a known problem with RDP connections on Windows 8 systems? Anything I should look for?

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• Minimize writes to SSD disks with Windows 7

  - by mark

  Most people use their SSD as their primary system installation disk with Windows 7. W7 already has a lot of optimizations for SSDs, both in terms of performance and lifetime. Minimizing writes increases the lifetime of SSDs, so post each suggestion as an answer and let others vote on them. Update: I'm not sure anymore that minimizing writes is a good thing [tm], hard facts that SSDs will degrade within a noticeable time are missing and it seems this it can create a bit FUD about the functionality of the SSD. In other words: I question the usefulness of my wiki question.

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• Virtualbox, slow upload speed using nat

  - by user1622094

  Im running Virtualbox on a Ubuntu 12.04 server (host) and I'm running a Windows 7 as guest os. Im using the (virtual) Intel PRO/1000 MT network card. I get good network performance for download using both nat and bridged network settings but upload speed is really slow using nat. I have tied this on tow different servers, one brand new, and one a several years old, both gave the same result. If you can explain this behavior or have ideas of further test I can perform please let me know.

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• How do I log file system read/writes by filename in Linux?

  - by Casey

  I'm looking for a simple method that will log file system operations. It should display the name of the file being accessed or modified. I'm familiar with powertop, and it appears this works to an extent, in so much that it show the user files that were written to. Is there any other utilities that support this feature. Some of my findings: powertop: best for write access logging, but more focused on CPU activity iotop: shows real time disk access by process, but not file name lsof: shows the open files per process, but not real time file access iostat: shows the real time I/O performance of disk/arrays but does not indicate file or process

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• How can I deactivate the gnome desktop of my ubuntu server?

  - by 19 Lee

  I'm running a home server on my old laptop (atom cpu). I installed ubuntu 12.04 server edition, but I also installed ubuntu-desktop. So, when I turn it on, ubuntu desktop is shown. I sometimes use GUI, but I want to turn the ubuntu-desktop (gnome-desktop) off when I don't use it. I think I can save resources by turning off the GUI. It's necessary since my laptop's performance is not very good and it often becomes very hot. I guess I can run ubuntu-desktop on my terminal with "startx" command. But, I don't know how to turn the X window off for a moment. Anybody have an idea? Thanks in advance.

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• Why using swap file over a SMB/NFS mounted filesystem is not possible in Linux?

  - by Avio

  I'd like to use another machine's unused RAM as swapspace for my primary Linux installation. I was just curious about performance of network ramdisks compared to local (slow) mechanical hard disks. The swapfile is on a tmpfs mountpoint and is shared through samba. However, every time I try to issue: swapon /mnt/ramswap/swapfile I get: swapon: /mnt/ramswap/swapfile: swapon failed: Invalid argument and in dmesg I read: [ 9569.806483] swapon: swapfile has holes I've tried to allocate the swapfile with dd if=/dev/zero of=swapfile bs=1024 (but also =4096 and =1048576) and with truncate -s 2G (both followed by mkswap swapfile) but the result is always the same. In this post (dated back to 2002) someone says that using a swapfile over NFS/SMB is not possible in Linux. Is this statement still valid? And if yes, what is the reason of this choice and is there any workaround to have this working?

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• Is running multiple databases on login going to make my Mac really slow?

  - by Walrus the Cat

  Sometime ago, I installed Postgres, and the Launch agent that causes it to run when I log in. Just now, I did the same thing for Mongo. I was just about to do it for Couch. I don't remember if I ever did it for MySQL, but I probably did. Mongo and Couch are just 'when I have time to look into it' sort of things, but I don't want to have to remember to start them when I do. I have a 2.4 Ghz processor and 8 GB ram. Is this sort of behavior going to significantly impact my computer's performance? Should I be scrambling to uninstall all but the database I'm currently using, or can I install all the things and run them all the time? Thanks

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• How is it possible for SSD's drives to have such a good latency?

  - by tigrou

  First time i read some information about SSD's, i was surprised to learn they internally use NAND flash chips. This kind of memory is generally slow (low bandwidth) and have high latency while SSD's are just the opposite. But here is how it works : SSD drives increase their bandwidth by using several NAND flash chips in parallel. In other words, they do some data striping (aka RAID0) across several chips (done by the controller). What i don't understand is how SSD's drives have such a low latency, whereas they are using NAND chips? (or at least lot better than what a typical single NAND chip would do) EDIT: I think under-estimate NAND chip capabilities. USB drives, while powered by NAND's are mostly limited by USB protocol (which have a pretty high latency) and the USB controller. That explain their poor performance in some cases.

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• When adding second processor to SQL Server, will it automatically balance the load?

  - by ddavis

  We have a SQL Server 2008 R2 (10.5) on a dedicated box with a single 2.4Ghz processor, which regularly runs at 70-80% CPU. We are going to be adding a significant number of users to the application and therefore want to add a second processor to the box (scale up). Will SQL Server automatically use the second processor to balance threads, or is there additional configuration that will need to be done? In other words, will adding the second processor drop my CPU usage to 35-40% per CPU, automatically balancing the load? Based on what I read here, it seems that it will: http://msdn.microsoft.com/en-us/library/ms181007.aspx However, I've read elsewhere that CPU performance gains can be made by assigning database tables to different filegroups, but I'm not sure we want to get that complicated at this point.

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