Can you go into some more detail on how you set up ZFS on these systems?
Robert Treat
conjecture: xzilla.net
consulting: omniti.com
On Tue, Sep 13, 2011 at 10:56 PM, Andy Colson <andy@squeakycode.net> wrote:
> On 09/13/2011 08:15 PM, Toby Corkindale wrote:
>>
>> Hi,
>> Some months ago, I ran some (probably naive) benchmarks looking at how
>> pgbench performed on an identical system with differing filesystems. (on
>> Linux).
>>
>> Since then the kernel-level version of ZFS became usable, and there have
>> been improvements to btrfs, and no doubt various updates in the Linux kernel
>> and PostgreSQL that should help performance.
>>
>> I ran the tests on Ubuntu 11.04 with Pg 9.0 first, then upgraded the
>> system to Ubuntu 11.10 (beta) with Pg 9.1 and ran them again.
>>
>> The latter combination showed a considerable performance improvement
>> overall - although I didn't investigate to find out whether this was due to
>> kernel improvements, postgres improvements, or virtio improvements.
>>
>> The results are measured in transactions-per-second, with higher numbers
>> being better.
>>
>> Results:
>>
>> ext4 (data=writeback,relatime):
>> natty: 248
>> oneiric: 297
>>
>> ext4 (data=writeback,relatime,nobarrier):
>> natty: didn't test
>> oneiric: 1409
>>
>> XFS (relatime):
>> natty: didn't test
>> oneiric: 171
>>
>> btrfs (relatime):
>> natty: 61.5
>> oneiric: 91
>>
>> btrfs (relatime,nodatacow):
>> natty: didn't test
>> oneiric: 128
>>
>> ZFS (defaults):
>> natty: 171
>> oneiric: 996
>>
>>
>> Conclusion:
>> Last time I ran these tests, xfs and ext4 pulled very similar results, and
>> both were miles ahead of btrfs. This time around, ext4 has managed to get a
>> significantly faster result than xfs.
>>
>> However we have a new contender - ZFS performed *extremely* well on the
>> latest Ubuntu setup - achieving triple the performance of regular ext4!
>> I'm not sure how it achieved this, and whether we're losing some kind of
>> data protection (eg. like the "barrier" options in XFS and ext4).
>> If ext4 has barriers disabled, it surpasses even ZFSs high score.
>>
>> Oddly, ZFS performed wildly differently on ubuntu 11.04 vs 11.10b. I can't
>> explain this. Any ideas?
>>
>>
>> Cheers,
>> Toby
>>
>
> Did you test unplugging the power cable in the middle of a test to see which
> would come back up?
>
> -Andy
>
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