Scott Otis wrote:
I agree that they don't make sense - part of the reason I am looking for
help :)
I am using iostat to get those numbers ( which I specify to average over
5 min then collect to display in Cacti ).
2 processes are taking up a good deal of CPU - the postgres stats
collector and autovacuum ones. Both of those are using a lot of 1 core
each.
I am not familiar with a dd test - what is that?
Thanks,
Scott
On Sep 3, 2009, at 8:03 AM, "Andy Colson" <andy@xxxxxxxxxxxxxxx> wrote:
Scott Otis wrote:
Would love to get some advice on how to change my conf settings /
setup to get better I/O performance.
Total I/O (these number are pretty constant throughout the day):
Reads: ~ 100 / sec for about 2.6 Mb/sec
Writes: ~ 400 /sec for about 46.1Mb/sec
Most of the SQL happening is selects – very little inserts, updates
and deletes comparatively.
Maybe I'm wrong, but those two don't seem to jive. You say its mostly
selects, but you show higher writes per second.
Does freebsd have a vmstat or iostat? How did you get the numbers
above? How's the cpu's look? (are they pegged?)
The io stats above seem low (reading 2 meg a second is a tiny
fraction of what your system should be capable of). Have you tried a
dd test?
-Andy
Please keep the list included so others may help.
the dd test:
http://www.westnet.com/~gsmith/content/postgresql/pg-disktesting.htm
I think Ivan is right, the 2 meg a second is probably because most of the reads are from cache. But he and I looked at the writes differently. If we ignore the 400/sec, and just read 46 meg a second (assuming you meant megabyte and not megabit) then, that's pretty slow (for sequential writing) -- which the dd test will measure your sequential read and write speed.
Ivan asked a good question:
By the way, why do you think your setup is slow? Is your application slow and you think your database is the reason?
-Andy
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