On Thu, 5 Apr 2007, Scott Marlowe wrote:
I've read some recent contrary advice. Specifically advising the
sharing of all files (pg_xlogs, indices, etc..) on a huge raid array
and letting the drives load balance by brute force.
The other, at first almost counter-intuitive result was that putting
pg_xlog on a different partition on the same array (i.e. one big
physical partition broken up into multiple logical ones) because the OS
overhead of writing all the data to one file system caused performance
issues. Can't remember who reported the performance increase of the top
of my head.
I noticed this behavior on the last Areca based 8 disk Raptor system I built.
Putting pg_xlog on a separate partition on the same logical volume was faster
than putting it on the large volume. It was also faster to have 8xRAID10 for
OS+data+pg_xlog vs 6xRAID10 for data and 2xRAID1 for pg_xlog+OS. Your
workload may vary, but it's definitely worth testing. The system in question
had 1GB BBU.
--
Jeff Frost, Owner <jeff@xxxxxxxxxxxxxxxxxxxxxx>
Frost Consulting, LLC http://www.frostconsultingllc.com/
Phone: 650-780-7908 FAX: 650-649-1954
