From: Osumi, Takamichi/大墨 昂道 <osumi.takami...@fujitsu.com> > I executed each wal_level three times and calculated the average time > and found that disabling WAL logging reduced about 73 % of the minimal's > loading speed > in this test. This speed-up came from the difference of generated WAL sizes.
So, it's 4x speedup when the WAL buffer and/or disk is likely to be saturated. That's nice! > In this test, to load the data generated more than 10GB of WALs with > wal_level=minimal > while wal_level=none emits just 760 bytes of WALs. > > I expect this size for none will become smaller when > I take the modification to filter out the types of WAL which is discussed > above. I don't expect so, because the WAL volume is already very small in this workload (probably only the commit records.) > Also, I monitored numbers of iostat's 'util' and noticed that > util's spike to use I/O reduced from twice to once when I changed the level > from minimal to none, which should be the effect of the patch. It's a bit mysterious. I thought %util would be constantly 100% when wal_level = minimal. That may be because wal_buffers is large. Regards Takayuki Tsunakawa
