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
differingfilesystems. (on Linux).
>
> Since then the kernel-level version of ZFS became usable, and there have been improvements to btrfs, and no doubt
variousupdates 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
ranthem again.
>
> The latter combination showed a considerable performance improvement overall - although I didn't investigate to find
outwhether 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
performanceof regular ext4!
> I'm not sure how it achieved this, and whether we're losing some kind of data protection (eg. like the "barrier"
optionsin 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
