This is a spill over from some discussions on some of the FreeBSD
mailing lists about FS performance. After FreeBSD 4.5-RELEASE, the
file system block size was bumped from 8K to 16K. Right now,
PostgreSQL still stores data in 8K blocks. Are there any objections
to me increasing the block size for FreeBSD installations to 16K for
the upcoming 7.4 release?
'bout the only reason I can think of to _not_ increase the block size
for FreeBSD would be if someone was mounting PGDATA on an ext2
partition. :-P
Early performance tests on my laptop suggest it's about 8% faster for
writing when both the FS and PostgreSQL use 16K blocks. From my tests
loading a database:
With 8K blocks:
15.188u 3.404s 7:12.27 4.2% 209+340k 1251+0io 0pf+0w
14.867u 3.686s 7:32.54 4.0% 201+327k 1252+0io 0pf+0w
avg wall clock sec to complete: 442
With 16K blocks:
15.192u 3.312s 6:44.43 4.5% 198+322k 1253+0io 0pf+0w
15.120u 3.330s 6:51.43 4.4% 205+334k 1254+0io 0pf+0w
avg wall clock sec to complete: 407
I'll take the 35sec/8% speedup any day of the week and twice on
Sunday. Granted these tests were done on my laptop and were 100%
write. If someone wants to do some good read tests, I'd be interested
in those results to see if it's still 8% faster. In using 16K blocks,
I'd imagine this'll make using seq scans cheaper on FreeBSD.
Comments? -sc
--
Sean Chittenden