are there any other xfs settings that should be tuned for postgres? I see this post mentions "allocation groups." does anyone have suggestions for those settings? http://archives.postgresql.org/pgsql-admin/2009-01/msg00144.php what about raid stripe size? does it really make a difference? I think the default for the perc is 64kb (but I'm not in front of the server right now). -Whit On Tue, Apr 28, 2009 at 7:40 PM, Scott Carey <scott@xxxxxxxxxxxxxxxxx> wrote: > On 4/28/09 11:16 AM, "Craig James" <craig_james@xxxxxxxxxxxxxx> wrote: > >> Kenneth Marshall wrote: >>>>> Additionally are there any clear choices w/ regard to filesystem >>>>> types? ?Our choices would be xfs, ext3, or ext4. >>>> Well, there's a lot of people who use xfs and ext3. XFS is generally >>>> rated higher than ext3 both for performance and reliability. However, >>>> we run Centos 5 in production, and XFS isn't one of the blessed file >>>> systems it comes with, so we're running ext3. It's worked quite well >>>> for us. >>>> >>> >>> The other optimizations are using data=writeback when mounting the >>> ext3 filesystem for PostgreSQL and using the elevator=deadline for >>> the disk driver. I do not know how you specify that for Ubuntu. >> >> After a reading various articles, I thought that "noop" was the right choice >> when you're using a battery-backed RAID controller. The RAID controller is >> going to cache all data and reschedule the writes anyway, so the kernal >> schedule is irrelevant at best, and can slow things down. >> >> On Ubuntu, it's >> >> echo noop >/sys/block/hdx/queue/scheduler >> >> where "hdx" is replaced by the appropriate device. >> >> Craig >> > > I've always had better performance from deadline than noop, no matter what > raid controller I have. Perhaps with a really good one or a SAN that > changes (NOT a PERC 6 mediocre thingamabob). > > PERC 6 really, REALLY needs to have the linux "readahead" value set up to at > least 1MB per effective spindle to get good sequential read performance. > Xfs helps with it too, but you can mitigate half of the ext3 vs xfs > sequential access performance with high readahead settings: > > /sbin/blockdev --setra <value> <device> > > Value is in blocks (512 bytes) > > /sbin/blockdev --getra <device> to see its setting. Google for more info. > >> >> -- >> Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) >> To make changes to your subscription: >> http://www.postgresql.org/mailpref/pgsql-performance >> > > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
