On Thu, Jun 24, 2010 at 5:14 AM, Matthew Wakeling <matthew@xxxxxxxxxxx> wrote: > 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. This is not strictly true of the WAL, which writes sequentially and more than one transaction at a time. As you said though, test it to be sure. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
