From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: pgsql-performance@postgresql.org
Subject: wal_synch_method = open_sync safe on RHEL 5.5?
Date: Fri, 18 Jun 2010 13:39:43 +1200
Message-ID: <4C1ACE5F.1080802@catalyst.net.nz> (raw)
Some more on the RHEL 5.5 system I'm helping to setup. Some benchmarking
using pgbench appeared to suggest that wal_sync_method=open_sync was a
little faster than fdatasync [1]. Now I recall some discussion about
this enabling direct io and the general flakiness of this on Linux, so
is the option regarded as safe?
[1] The workout:
$ pgbench -i -s 1000 bench
$ pgbench -c [1,2,4,8,32,64,128] -t 10000
Performance peaked around 2500 tps @32 clients using open_sync and 2200
with fdatasync. However the disk arrays are on a SAN and I suspect that
when testing with fdatasync later in the day there may have been
workload 'leakage' from other hosts hitting the SAN.
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To: pgsql-performance@postgresql.org
Cc: mark.kirkwood@catalyst.net.nz
Subject: Re: wal_synch_method = open_sync safe on RHEL 5.5?
In-Reply-To: <4C1ACE5F.1080802@catalyst.net.nz>
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