Wow, thanks for doing this!
In general, your tests seem to show that there isn't a substantial
penalty for using ZFS as of version 8.0.
If you have time for more tests, I'd like to ask you for a few more tweaks:
(1) change the following settings according to conventional wisdom:
wal_buffers = 8MB
effective_cache_size = 9GB
checkpoint_segments = 32
on ZFS only: full_page_writes=off
(2) What scale were you using for the pgbench database? I didn't see it
in the e-mail. It would be worth testing:
s = 10 (small database, in memory)
s = 500 (7GB, ram mostly full)
s = 1000 (14GB, slightly larger than ram)
s = 3000 (43GB, much larger than ram)
If you were only testing a small size in your runs, then the only
Filesystem behavoir you were testing was the transaction log.
(3) Try a ZFS 128K record size
(4) Centos/Ext3 appears to have had better staying power with high
numbers of clients. Can you continue testing with 50, 100 and 200
clients on that combination? And with data=writeback,noatime on Ext3?
-- Josh Berkus
PostgreSQL Experts Inc.
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