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.