On Wed, 23 Jun 2010, Scott Marlowe wrote:
We have a 12 x 600G hot swappable disk system (raid 10)
and 2 internal disk ( 2x 146G)
Does it make sense to put the WAL and OS on the internal disks
So for us, the WAL and OS and logging on the same data set works well.
Generally, it is recommended that you put the WAL onto a separate disc to
the data. However, in this case, I would be careful. It may be that the 12
disc array is more capable. Specifically, it is likely that the 12-disc
array has a battery backed cache, but the two internal drives (RAID 1
presumably) do not. If this is the case, then putting the WAL on the
internal drives will reduce performance, as you will only be able to
commit a transaction once per revolution of the internal discs. In
contrast, if the WAL is on a battery backed cache array, then you can
commit much more frequently.
Test it and see.
Matthew
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