On Thu, 7 Aug 2008, Henrik wrote:
My first idea was to have one partition on the RAID 10 using ext3 with
data=writeback, noatime as mount options.
But I wonder if I should have 2 partitions on the RAID 10 one for the PGDATA
dir using ext3 and one partition for XLOGS using ext2.
Really depends on your write volume. The write cache on your controller
will keep having a separate xlog disk from being as important as it is
without one. If your write volume is really high though, it may still be
a bottleneck, and you may discover your app runs better with a dedicated
ext2 xlog disk instead.
The simple version is:
WAL write volume extremely high->dedicated xlog can be better
WAL volume low->more disks for the database array better even if that
mixes the WAL on there as well
If you want a true answer for which is better, you have to measure your
application running on this hardware.
6 SAS 15K drives in RAID 10 on one of the SAN controllers for database
With only 6 disks available, in general you won't be able to reach the WAL
as a bottleneck before being limited by seeks on the remaining 4 database
disks, so you might as well group all 6 together. It's possible your
particular application might prefer it the other way though, if you're
doing a while lot of small writes for example. I've seen a separate WAL
handle low-level benchmarks better, but on more real-world loads it's
harder to run into that situation.
--
* Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD
