|To:||Peter Grandi <pg_xf2@xxxxxxxxxxxxxxxxxx>|
|Subject:||Re: XFS use within multi-threaded apps|
|From:||Angelo McComis <angelo@xxxxxxxxxxx>|
|Date:||Sat, 23 Oct 2010 16:59:06 -0400|
|Cc:||Linux XFS <xfs@xxxxxxxxxxx>|
|References:||<AANLkTi=w1o8EF6-M7o8Qi9VpY-10m+MCR8U+K1_Aze=g@xxxxxxxxxxxxxx> <87eibm4xon.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <AANLkTikqHvSmr=WSZ3t8m3wKOGcUmQQ1v9Qx9MqGArS+@xxxxxxxxxxxxxx> <19651.15840.54770.942761@xxxxxxxxxxxxxxxxxx>|
On Sat, Oct 23, 2010 at 3:56 PM, Peter Grandi <pg_xf2@xxxxxxxxxxxxxxxxxx> wrote:|
True - the benchmarks themselves don't tell a complete story. Specific to iozone, I was basically comparing XFS to EXT3, and showing the results (various record sizes, various file sizes, and various worker thread counts)... The only true benchmark is to run the application in the way that is characteristic of how it will be used. Database benchmarks themselves would vary greatly between use cases: from generic looking up data (random reads), data warehouse analytics (sequential reads), ETL (sequential reads, sequential writes), etc.
Peter, and others:
Thanks for this great discussion. I appreciate the thought that went into all of the replies.
In the end, we had a sit down discussion with our vendor. They admitted that they "support" XFS, but have very few customers using it (said they can count them on one hand), and when I pressed them on if it's a technology limitation, they threw down the gauntlet and said "look, we're giving you our frank recommendation here. EXT3." They quoted as having 10+TB databases running OLTP transactions on XFS, with 4-5GB/sec sustained throughput to the disk system. And 20-30TB for data warehouse type operations. When pressed about the cache flush issue, they mentioned they use direct IO under ext3, and it's not an issue in that case.
In doing my research, I searched for references of other Fortune nn-sized companies who use this DB and use XFS underneath it. I came up empty handed... I searched my network for large-ish companies using XFS, and how they were using it. I'm not sure if we're bordering on "secret sauce" type stuff here, but I had an extremely difficult time getting enterprise references to back up the research I've done.
For our use, we had to opt to follow the vendor recommendation, and it came down to not wanting to be one of those that they can count on one hand using XFS with their product.
I'm still confounded by why - when XFS is technically superior in these cases - is it so obscure? Are Enterprise Linux guys just not looking this deep under the covers to uncover performance enhancements like this? Is it because RedHat didn't to include the XFS tools in the distro until recently, causing XFS to not be a choice part of it? Are other Linux folks "next, next, finish..." people when it comes to how they install? I really don't get it.
Thanks for all the discussion folks. I hope to put forth other use cases as the surface.
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