Comments on: SSD, XFS, LVM, fsync, write cache, barrier and lost transactions http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/ Percona's MySQL & InnoDB performance and scalability blog Sat, 11 Feb 2012 16:45:54 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: SAB http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-872547 SAB Mon, 09 Jan 2012 22:06:01 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-872547 Sorry for digging this post up, but did you tried those tests with Sysbench ? I made a few tests with write cache on and off but I don't have a SSD to compare the results. Sorry for digging this post up, but did you tried those tests with Sysbench ? I made a few tests with write cache on and off but I don’t have a SSD to compare the results.

]]> By: Evan Jones http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-772380 Evan Jones Tue, 24 Aug 2010 13:05:49 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-772380 Note that according to my tests, the Intel X25-M G2 loses data even when the write cache is disabled. I have not tested the X25-E, but I suspect this may also be an issue there? See the following for more info: http://evanjones.ca/intel-ssd-durability.html Note that according to my tests, the Intel X25-M G2 loses data even when the write cache is disabled. I have not tested the X25-E, but I suspect this may also be an issue there? See the following for more info:

http://evanjones.ca/intel-ssd-durability.html

]]> By: Robert http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-744339 Robert Tue, 06 Apr 2010 21:08:40 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-744339 I know this posting s quite old, but it would be great to know the firmware of the Intel X25-E SSD you tested ? I know this posting s quite old, but it would be great to know the firmware of the Intel X25-E SSD you tested ?

]]> By: andor http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-712790 andor Thu, 21 Jan 2010 21:51:40 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-712790 Vadim, thats awesome.. that has did the trick for me! It says the cache is switched off .. I was tinkering around with the sdparm utility as I thought the device file 'sdc' starts with s. (one of my friends suggested this. He said that since we connected the SSD with a SAS controller, we should be using sdparm. I have no idea what this SAS controller is.) thanks a lot for the input. Vadim, thats awesome.. that has did the trick for me! It says the cache is switched off .. I was tinkering around with the sdparm utility as I thought the device file ‘sdc’ starts with s. (one of my friends suggested this. He said that since we connected the SSD with a SAS controller, we should be using sdparm. I have no idea what this SAS controller is.) thanks a lot for the input.

]]> By: Vadim http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-712788 Vadim Thu, 21 Jan 2010 21:41:59 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-712788 Andor, hdparm -W 0 /dev/sdb works for me. Output: /dev/sdb: setting drive write-caching to 0 (off) write-caching = 0 (off) Andor,

hdparm -W 0 /dev/sdb

works for me.

Output:

/dev/sdb:
setting drive write-caching to 0 (off)
write-caching = 0 (off)

]]> By: andor http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-712786 andor Thu, 21 Jan 2010 21:35:19 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-712786 Hi Vadim, I know that you published your thread long time back.. but I have a really really basic question. How do you turn off write cache on X25-E? I've searched everywhere how to do it but could only find studies showing performance drop after doing it. I used sdparm in the following fashion: sudo sdparm -s WCE=0 -S /dev/sdc but get an error like this: /dev/sdc: ATA SSDSA2SH032G1GN 045C change_mode_page: mode page indicates it is not savable but '--save' option given (try without it) The error seems to suggest we cannot switch the X25-E's cache.. but we know thats not the case. I am asking this question on the wrong forum I believe, but I thought you might have a ready solution for me.. Thanks andor. Hi Vadim,

I know that you published your thread long time back.. but I have a really really basic question. How do you turn off write cache on X25-E? I’ve searched everywhere how to do it but could only find studies showing performance drop after doing it. I used sdparm in the following fashion:

sudo sdparm -s WCE=0 -S /dev/sdc

but get an error like this:

/dev/sdc: ATA SSDSA2SH032G1GN 045C
change_mode_page: mode page indicates it is not savable but
‘–save’ option given (try without it)

The error seems to suggest we cannot switch the X25-E’s cache.. but we know thats not the case.

I am asking this question on the wrong forum I believe, but I thought you might have a ready solution for me..

Thanks
andor.

]]> By: Baron Schwartz http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-611795 Baron Schwartz Fri, 10 Jul 2009 01:41:23 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-611795 Peter [Eisentraut], I've been following your benchmark blog posts with a lot of interest, too :-) Peter [Eisentraut], I’ve been following your benchmark blog posts with a lot of interest, too :-)

]]> By: http://petereisentraut.blogspot.com/ http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-611212 http://petereisentraut.blogspot.com/ Thu, 09 Jul 2009 14:57:06 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-611212 I meant http://petereisentraut.blogspot.com/2009/07/solid-state-drive-benchmarks-and-write.html ... funny markup ... I meant http://petereisentraut.blogspot.com/2009/07/solid-state-drive-benchmarks-and-write.html … funny markup …

]]> By: http://petereisentraut.blogspot.com/ http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-611211 http://petereisentraut.blogspot.com/ Thu, 09 Jul 2009 14:55:52 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-611211 Somewhat after the fact I realized that this information relates closely with the SSD tests I did with PostgreSQL, reported here: . With a plain dd test I get about 50% performance loss when turning the write cache off on the X25-E. That's much better than the more than fourfold loss you are observing (if I parse your numbers right). I'm planning to do a pgbench test later, which might provide more insight. Somewhat after the fact I realized that this information relates closely with the SSD tests I did with PostgreSQL, reported here: . With a plain dd test I get about 50% performance loss when turning the write cache off on the X25-E. That’s much better than the more than fourfold loss you are observing (if I parse your numbers right). I’m planning to do a pgbench test later, which might provide more insight.

]]> By: Baron Schwartz http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/comment-page-1/#comment-530886 Baron Schwartz Mon, 06 Apr 2009 12:21:55 +0000 http://www.mysqlperformanceblog.com/?p=631#comment-530886 Oh, and the broad consensus in the room was "these things are worth a lot less if they lie to the operating system about durability, and a UPS is not an acceptable workaround" :-) Oh, and the broad consensus in the room was “these things are worth a lot less if they lie to the operating system about durability, and a UPS is not an acceptable workaround” :-)

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