
Resending this now the LUV list seems to be back up, as I never saw it come through yesterday. Apologies if this is a duplicate. -------- Original Message -------- Hi, Some months ago, I ran some (probably naive) benchmarks looking at how pgbench performed on an identical system with differing filesystems and mount options. Since then some of you have pointed out that ZFS is looking pretty good on Linux now, and I'm sure there's been a bunch of btrfs fixes too, 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. Perhaps some of you can shed some light on this for me? Oddly, ZFS performed wildly differently on ubuntu 11.04 vs 11.10b. I can't explain this, as the ZFS kernel module was identical (coming from a third-party apt repository). Any ideas? Cheers, Toby