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  • Various problems with software raid1 array built with Samsung 840 Pro SSDs

    - by Andy B
    I am bringing to ServerFault a problem that is tormenting me for 6+ months. I have a CentOS 6 (64bit) server with an md software raid-1 array with 2 x Samsung 840 Pro SSDs (512GB). Problems: Serious write speed problems: root [~]# time dd if=arch.tar.gz of=test4 bs=2M oflag=sync 146+1 records in 146+1 records out 307191761 bytes (307 MB) copied, 23.6788 s, 13.0 MB/s real 0m23.680s user 0m0.000s sys 0m0.932s When doing the above (or any other larger copy) the load spikes to unbelievable values (even over 100) going up from ~ 1. When doing the above I've also noticed very weird iostat results: Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 1589.50 0.00 54.00 0.00 13148.00 243.48 0.60 11.17 0.46 2.50 sdb 0.00 1627.50 0.00 16.50 0.00 9524.00 577.21 144.25 1439.33 60.61 100.00 md1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 0.00 1602.00 0.00 12816.00 8.00 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 And it keeps it this way until it actually writes the file to the device (out from swap/cache/memory). The problem is that the second SSD in the array has svctm and await roughly 100 times larger than the second. For some reason the wear is different between the 2 members of the array root [~]# smartctl --attributes /dev/sda | grep -i wear 177 Wear_Leveling_Count 0x0013 094% 094 000 Pre-fail Always - 180 root [~]# smartctl --attributes /dev/sdb | grep -i wear 177 Wear_Leveling_Count 0x0013 070% 070 000 Pre-fail Always - 1005 The first SSD has a wear of 6% while the second SSD has a wear of 30%!! It's like the second SSD in the array works at least 5 times as hard as the first one as proven by the first iteration of iostat (the averages since reboot): Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 10.44 51.06 790.39 125.41 8803.98 1633.11 11.40 0.33 0.37 0.06 5.64 sdb 9.53 58.35 322.37 118.11 4835.59 1633.11 14.69 0.33 0.76 0.29 12.97 md1 0.00 0.00 1.88 1.33 15.07 10.68 8.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 1109.02 173.12 10881.59 1620.39 9.75 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.41 0.01 3.10 0.02 7.42 0.00 0.00 0.00 0.00 What I've tried: I've updated the firmware to DXM05B0Q (following reports of dramatic improvements for 840Ps after this update). I have looked for "hard resetting link" in dmesg to check for cable/backplane issues but nothing. I have checked the alignment and I believe they are aligned correctly (1MB boundary, listing below) I have checked /proc/mdstat and the array is Optimal (second listing below). root [~]# fdisk -ul /dev/sda Disk /dev/sda: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00026d59 Device Boot Start End Blocks Id System /dev/sda1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sda2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sda3 4605952 814106623 404750336 fd Linux raid autodetect root [~]# fdisk -ul /dev/sdb Disk /dev/sdb: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0003dede Device Boot Start End Blocks Id System /dev/sdb1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sdb3 4605952 814106623 404750336 fd Linux raid autodetect /proc/mdstat root # cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdb2[1] sda2[0] 204736 blocks super 1.0 [2/2] [UU] md2 : active raid1 sdb3[1] sda3[0] 404750144 blocks super 1.0 [2/2] [UU] md1 : active raid1 sdb1[1] sda1[0] 2096064 blocks super 1.1 [2/2] [UU] unused devices: Running a read test with hdparm root [~]# hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 664 MB in 3.00 seconds = 221.33 MB/sec root [~]# hdparm -t /dev/sdb /dev/sdb: Timing buffered disk reads: 288 MB in 3.01 seconds = 95.77 MB/sec But look what happens if I add --direct root [~]# hdparm --direct -t /dev/sda /dev/sda: Timing O_DIRECT disk reads: 788 MB in 3.01 seconds = 262.08 MB/sec root [~]# hdparm --direct -t /dev/sdb /dev/sdb: Timing O_DIRECT disk reads: 534 MB in 3.02 seconds = 176.90 MB/sec Both tests increase but /dev/sdb doubles while /dev/sda increases maybe 20%. I just don't know what to make of this. As suggested by Mr. Wagner I've done another read test with dd this time and it confirms the hdparm test: root [/home2]# dd if=/dev/sda of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 38.0855 s, 282 MB/s root [/home2]# dd if=/dev/sdb of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 115.24 s, 93.2 MB/s So sda is 3 times faster than sdb. Or maybe sdb is doing also something else besides what sda does. Is there some way to find out if sdb is doing more than what sda does? UPDATE Again, as suggested by Mr. Wagner, I have swapped the 2 SSDs. And as he thought it would happen, the problem moved from sdb to sda. So I guess I'll RMA one of the SSDs. I wonder if the cage might be problematic. What is wrong with this array? Please help!

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  • On Mac OS X how can I monitor what is using my internet connection?

    - by Jon Hopkins
    I've got a relatively limited broadband connection (I live miles from the nearest exchange) and from time to time net access (but nothing else) slows to a near crawl. I know from a bit of monitoring software that the connection is being fairly heavily used which would explain it but I don't know what's using it. There are certainly plenty of things which might (these days there are dozens of apps that will either regularly or infrequently check data or download updates) but how can I find out? I'm happy to pay (a small amount of) money if needed, though in that case I'd rather it were a recommendation that me just Googling for something.

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  • Multiple columns in a single index versus multiple indexes

    - by Tim Coker
    The short version of my question is what's the difference between three indexes each indexing a single column and one index indexing three columns. Background follows. I'm primarily a programmer but have to do DBA work because we don't have a DBA. I'm evaluating our indexes versus the queries run against a particular table. The table as 3 columns that I'm often filtering against or getting the max value of. Most of the time the queries look like select max(col_a) from table where col_b = 'avalue' or select col_c from table where col_b = 'avalue' and col_a = 'anothervalue' All columns are independently indexed. My question is would I see any difference if I had an index that indexed col_b and col_a together since they can appear in a where clause together?

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  • Having munin server monitoring problem: Graphs not being generated.

    - by geerlingguy
    When I run munin-cron (munin-cron --debug), I get the following error: 2010/05/10 13:39:01 [WARNING] Call to accept timed out. Remaining workers: archstl.org;archstl.archstl.org 2010/05/10 13:39:01 [DEBUG] Active workers: 1/8 These errors simply keep repeating themselves until I quit munin-cron. I've followed the directions for debugging munin on the 'Debugging Munin plugins' wiki page, but I get the following results when going through their directions: After telnetting to localhost 4949, I can see a list of plugins, see a node at archstl.archstl.org, but can't fetch anything. The output is as follows: >fetch cpu . However, on the same machine (which is both the node and the master munin server), I can run munin-run cpu, and it prints the results correctly to the command line, like so: user.value 100829130 nice.value 3479880 system.value 13969362 idle.value 664312639 iowait.value 12180168 irq.value 14242 softirq.value 199526 steal.value 0 Looking at the wiki page mentioned above, it looks like it might be a plugin environment problem, but I can't figure out how to fix/change this... If the plugin does run with munin-run but not through telnet, you probably have a PATH problem. Tip: Set env.PATH for the plugin in the plugin's environment file.

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  • Can I change a MySQL table back and forth between InnoDB and MyISAM without any problems?

    - by Daniel Magliola
    I have a site with a decently big database, 3Gb in size, a couple of tables with a dozen million records. It's currently 100% on MyISAM, and I have the feeling that the server is going slower than it should because of too much locking, so I'd like to try going to InnoDB and see if that makes things better. However, I need to do that directly in production, because obviously without load this doesn't make any difference. However, I'm a bit worried about this, because InnoDB actually has potential to be slower, so the question is: If I convert all tables to InnoDB and it turns out i'm worse off than before, can I go back to MyISAM without losing anything? Can you think of any problems I might encounter? (For example, I know that InnoDB stores all data in ONE big file that only gets bigger, can this be a problem?) Thank you very much Daniel

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  • Is the "One Description Table to rule them all" approch good?

    - by DavRob60
    Long ago, I worked (as a client) with a software which use a centralized table for it's codified element. Here, as far as I remember, how the table look like : Table_Name (PK) Field_Name (PK) Code (PK) Sort_Order Description So, instead of creating a table every time they need a codified field, they where just adding row in this table with the new Table_Name and Field_Name. I'm sometime tempted to use this pattern in some database I design, but I have resisted to this as from now, I think there's something wrong with this, but I cannot put the finger on it. It is just because you land with some of the structure logic within the Data or something else?

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  • How should I store a Game Database on Android?

    - by Liam
    I'm looking at creating a game for Android and while I have most of the ins and outs worked out, the one thing I'm struggling with is how to store data for the game. Ultimately, the game will be based off of a lot of pre-defined data and statistics so the obvious choice to me would be something like SQLite, but as I'm pretty new to the realm of Android and Game Development, I'm not 100% certain if this is the right route to follow. The data will be general pre-defined data as well as player data (along the lines of careers stats - what place finished, etc). I was wondering if there was a better/best practice solution that wasn't SQLite and that would provide said functionality and if so, could you point me in the right direction?

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  • How do you debug why Windows is slow?

    - by aaron
    I've got Vista Biz and when my machine chugs I think it is because of paging, but I never know how to verify this. Procexp doesn't seem to provide useful information because it appears that nothing is going on when the chugs happen. perfmon seems like it has the counters I need, but I'm never sure what counters I should add to cover the information I want. For perfmon, I prefer numbers that are percents, so I can gauge load. Here are the counters I have up, but they don't always seem to correlate to chugs: - % disk time (logical) - page faults/sec (an indicator of lots of paging activity) - processor/%priviliged time

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  • easy visualization of usage statistics (web app)

    - by sova
    I have some usage queries for my web app's database, the results of which I want to display graphically. Is there an easy-to-use api that exists for this purpose? I want to show things like average query-time per user (a small user-base), average query time per day, and things like that. I think it would be cool to show these on a two-axis graph. I am displaying this data on my site, so a jQuery/javascript/html solution for rendering information into graphs would be ideal. Thank you :) P.S. I wasn't sure if I should ask this on SO, but I am looking more for which product to use, not how to program with it.

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  • GNOME/KDE Linux entirely in RAM?

    - by František Žiacik
    Hi. I'd like to have very responsive linux but I also like modern, elegant and functional desktops like gnome or kde, not the lightweight ones like xfce or lxde. Once I tried PuppyLinux and was impressed by the responsivity when I clicked an application. In my Ubuntu, it bothers me much when I click chromium and must wait 5 seconds of disk flashing until main window appears. Or evolution or anything else. Is it possible to make GNOME or KDE run entirely in RAM like PuppyLinux (of course, I mean frequently used applications and services, not all) if you have enough of it? I don't care if boot time is longer. I tried using "preload" but it didn't help much.

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  • Diagnostic high load sys cpu - low io

    - by incous
    A Linux server running Ubuntu 12.04 LTS with LAMP has a strange behaviour since last week: - cpu %sys higher than before, nearly equal %usr (before that, %sys just little compare with %usr) - IO reduce by half or 1/3 compare with the week before I try to diagnostic the process/cpu by some command (top/vmstat/mpstat/sar), and see that maybe it's a bit high on interrupt timer/resched. I don't know what that means, now open to any suggestion.

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  • Zenoss: Getting SNMP stats over SSH

    - by normalocity
    I have the SSH connection working. I have it successfully modeling the device (Ubuntu Server, in this case). What I can't get to work is the SNMP portion. It sounds like I have to custom add the snmpwalk command when doing monitoring over SSH - in other words, have Zenoss connect via SSH, and then run an arbitrary command agains the client (in this case, an snmpwalk), and then parse the results. What I need help doing is: Add the snmpwalk command to the SSH monitoring Parsing the output and getting the data back into the charts

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  • Important hardware components to avoid bottlenecks/improve speed on a laptop?

    - by joelhaus
    Looking for a powerful general use (including web development) laptop running Windows. Price points seem to be all over the place. Many less powerful machines are priced much higher than machines with better specs. How does one navigate this market? Are there any unpublished/under-publicized specs/bottlenecks you look for? Understanding that hardware improves over time, is there an efficient ratio that can be used (or something similar, like Windows Experience Index?) which will indicate how powerful a system is? Thanks in advance! P.S. Here is an example from a laptop released on September 17, 2010. Can anyone pick apart these specs? Is there missing information you would be looking for? OS: Win 7 Display: 16.4" LED backlit Processor: Intel Core i7-740QM, 6MB L3 Cache RAM: 6GB DDR3 1333MHz (8GB max.) Graphics: NVIDIA GeForce GT 425M (1 GB of dedicated DDR3) HDD: 500GB 7200RPM SATA Hard Drive Removable Disc: Blue-ray with DVD±R/RW Misc: webcam/mic/speakers/bluetooth (via Sony Vaio VPC-F137FX/B)

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  • How to tell if linux disk IO is causing excessive (> 1 second) application stalls

    - by noahz
    I have a Java application performing a large volume (hundreds of MB) of continuous output (streaming plain text) to about a dozen files a ext3 SAN filesystem. Occasionally, this application pauses for several seconds at a time. I suspect that something related to ext3 vsfs (Veritas Filesystem) functionality (and/or how it interacts with the OS) is the culprit. What steps can I take to confirm or refute this theory? I am aware of iostat and /proc/diskstats as starting points. Revised title to de-emphasize journaling and emphasize "stalls" I have done some googling and found at least one article that seems to describe behavior like I am observing: Solving the ext3 latency problem Additional Information Red Hat Enterprise Linux Server release 5.3 (Tikanga) Kernel: 2.6.18-194.32.1.el5 Primary application disk is fiber-channel SAN: lspci | grep -i fibre 14:00.0 Fibre Channel: Emulex Corporation Saturn-X: LightPulse Fibre Channel Host Adapter (rev 03) Mount info: type vxfs (rw,tmplog,largefiles,mincache=tmpcache,ioerror=mwdisable) 0 0 cat /sys/block/VxVM123456/queue/scheduler noop anticipatory [deadline] cfq

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  • Firefox takes a really long time to load some sites on Ubuntu

    - by Dave
    Hello guys, I have an issue here. Some sites - just a few - takes a really long time to load on Firefox. One example is A List Apart (http://www.alistapart.com/) which takes more than 30 minutes (yes, minutes, not seconds). On Opera, ou even through a telnet session, the problematic sites run without problem, fast as expected. I am using Linux 8.04, running Firefox 3.6.3 downloaded from mozilla site, with a 10M ADSL connection. I tried many tweaks I found googling, like disable IPv6, and change http pipelining settings on FF's about:config. None worked. I also used Firebug to find what phase during negotiation is the bottleneck. Findings are in the screenshot. Well guys, any idea what is the issue? And how to solve it? I repeat, this only happens with firefox (3.6.3 and prior versions), for a few sites only (even sites with much more requests, images, javascripts, stylesheets work fine), and http pipelines and IPv6 tweaks on about:config didn't work. Thanks

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  • SQL Saturday 40 - South Florida - July 31st 2010

    - by Herve Roggero
    Hi everyone - if you live in Florida, or if you will be in the area on July 31st come and see us! If would like to speak or attend, visit http://www.sqlsaturday.com/40/eventhome.aspx.  The event will be in Miramar, Florida - no too far from Fort Lauderdale. We had over 350 people show up last year and we will do better this year! We are also welcoming sponsors for this event. Thank you for spreading the word!

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  • Run serveral daemon using python

    - by ylc
    I noticed that serveral daemon invoked python seperately. For example, I have both wicd and ibus daemon running on my machine. Instead of launching a single instance of python, the daemons run with two python instance at the same time in htop: /usr/bin/python2 -O /usr/share/wicd/daemon/monitor.py python2 /usr/share/ibus/ui/gtk/main.py Is it a waste of doing that? If yes, how can I improve this? If no, why avoid putting all daemons run on a single python instance?

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  • How to interpret IOZone results?

    - by homer5439
    Here are the resuts of running IOZone on an ext3 filesystem on an LVM volume residing on a SAN LUN (it was ran with 5 parallel processes). "Throughput report Y-axis is type of test X-axis is number of processes" "Record size = 4 Kbytes " "Output is in Kbytes/sec" " Initial write " 81628.55 " Rewrite " 83354.72 " Read " 115595.02 " Re-read " 119306.09 " Reverse Read " 47684.20 " Stride read " 10011.09 " Random read " 16751.27 " Mixed workload " 5659.77 " Random write " 1661.85 " Pwrite " 36030.83 Now this is all nice and dandy, but my question is: how do I know whether the values are as good as they could be or there is something to tweak (and if so, what?) The actual usage I will have for that Logical Volume is to act as virtual disk for a VM.

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  • 503 error Varnish cache when eAccelerator is started

    - by Netismine
    I have a Magento installation running on x-large Amazon server. I have Varnish, memcached and eAccelerator installed on the server. At first everything was working fine, but then at some point it stopped working, throwing 503 error with Varnish cache stamp below it. When I disable eaccelerator, error is gone and site is working. This is my eaccelerator config: extension="eaccelerator.so" eaccelerator.shm_size = "512" eaccelerator.cache_dir = "/var/cache/php-eaccelerator" eaccelerator.enable = "1" eaccelerator.optimizer = "1" eaccelerator.debug = 0 eaccelerator.log_file = "/var/log/httpd/eaccelerator_log" eaccelerator.name_space = "" eaccelerator.check_mtime = "1" eaccelerator.filter = "" eaccelerator.shm_ttl = "0" eaccelerator.shm_prune_period = "0" eaccelerator.shm_only = "0" eaccelerator.allowed_admin_path = "" any hints?

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  • How to configure an ASUS motherboard.

    - by Absolute0
    I have an ASUS P7P55-M motherboard running with an Intel Core i5-750 processor and 4 GB RAM with 1600 MT/s speed. For some reason the default settings of the motherboard make all the components run at half their optimums. I have switched to the "D.O.C.P." profile and supposedly everything is as it's supposed to be (verified with CPU-Z). There is also an "X.M.P." profile and a manual one. Are either of the DOCP or XMP safe to go with? I wouldn't use the manual mode as I would likely mess something up real bad. XMP seems to be more memory oriented.

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  • “NT AUTHORITY\ANONYMOUS LOGON” error in Windows 7 (ASP.NET & Web Service)

    - by Tony_Henrich
    I have an asp.net web app which works fine in Windows XP machine in a domain. I am porting it to a Windows 7 stand alone machine. The app uses a web service which makes a call to sql server. The web server (IIS 7.5) and SQL Server are on the same stand alone machine. I enabled Windows authentication for the website and web service. The web service uses a trusted connection connection string. The web service credentials uses System.Net.CredentialCache.DefaultCredentials. I noticed username, password and domainname are blank after the call! The webservice and web site use the 'Classic .NET AppPool' with NetworkServices identity. I am getting an exception "NT AUTHORITY\ANONYMOUS LOGON" in the database call in the web service. I am assuming it's related to the blank credentials. I am expecting ASPNET user to be the security token to the database. Why is this not happening? Did I miss a setting? (Usually this happens when sql server and web server are on two different machines in a domain, delegation & double hopping, but in my case everything is on a dev box)

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  • Weblogic Threads Usage

    - by Hila
    I have an application deployed on WebLogic 10.3, which exhibits a strange behavior. I am running a constant (not too high) load on my application (20 concurrent users, running a light activity). The response time is reasonable (well below 100ms after the application stabilizes) Memory consumption seems fine (My application creates a lot of short-living objects, but they are garbaged collected so the overall memory consumption stays under 500 mb). Threads stats seem healthy as well: And yet, after I leave my test running for a while, more and more execute threads ("[ACTIVE] ExecuteThread: '3' for queue: 'weblogic.kernel.Default (self-tuning)'") are created, until eventually the application crashes: This test hasn't been running for a long time (All the new threads that you don't see in the first screenshot were created while I was writing this question), and I've seen much more threads being created. Any idea why these threads are being created?

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