On 29/11/2012 17:33, Merlin Moncure wrote:
one thing that immediately jumps out here is that your wal volume
could be holding you up. so it's possible we may want to move wal to
the ssd volume. if you can scrounge up a 9.2 pgbench, we can gather
more evidence for that by running pgbench with the "--unlogged-tables"
option, which creates the tables unlogged so that they are not wal
logged (for the record, this causes tables to be truncated when not
shut down in clean state).
Ok, got myself a 9.2 version of pgbench and run it a few times on
unlogged tables...
changing the number of threads has maybe a 5% change in values which
isn't probably too much to worry about.
-j 25 -c 100 -s 100 gives a tps of around 10.5k
using -N ups that to around 20k
using -S ups that again to around 40k
I'll have to wait until I get to shut the db down again to try the wal
on an ssd. Although unless I did something wrong it didn't seem to make
a huge difference before....
During these tests, iowait dropped to almost 0, user and sys stayed
around the same (60% and 20% respectively). although the disk traffic
was only in the 10s of Mb/s which seems very low - unless there is some
wierd caching going on and it gets dumped at a later date?
John
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