On Fri, Jul 15, 2011 at 12:34 AM, chris <chricki@gmx.net> wrote:
> I was thinking to put the WAL and the indexes on the local disks, and
> the rest on the SAN. If funds allow, we might downgrade the disks to
> SATA and add a 50 GB SATA SSD for the WAL (SAS/SATA mixup not possible).
Just to add to the conversation, there's no real advantage to putting
WAL on SSD. Indexes can benefit from them, but WAL is mosty
seqwuential throughput and for that a pair of SATA 1TB drives at
7200RPM work just fine for most folks. For example, in one big server
we're running we have 24 drives in a RAID-10 for the /data/base dir
with 4 drives in a RAID-10 for pg_xlog, and those 4 drives tend to
have the same io util % under iostat as the 24 drives under normal
usage. It takes a special kind of load (lots of inserts happening in
large transactions quickly) for the 4 drive RAID-10 to have more than
50% util ever.