On Tuesday 29 December 2009 00:06:28 Tom Lane wrote: > Andres Freund <andres@xxxxxxxxxxx> writes: > > This speeds up CREATE DATABASE from ~9 seconds to something around 0.8s > > on my laptop. Still slower than with fsync off (~0.25) but quite a > > worthy improvement. > > I can't help wondering whether that's real or some kind of > platform-specific artifact. I get numbers more like 3.5s (fsync off) > vs 4.5s (fsync on) on a machine where I believe the disks aren't lying > about write-complete. It makes sense that an fsync at the end would be > a little bit faster, because it would give the kernel some additional > freedom in scheduling the required I/O, but it isn't cutting the total > I/O required at all. So I find it really hard to believe a 10x speedup. I only comfortably have access to two smaller machines without BBU from here (being in the Hacker Jeopardy at the ccc congress ;-)) and both show this behaviour. I guess its somewhat filesystem dependent. Andres -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
