What would you recommend to do a quick test for this? (i.e WAL on internal disk vs WALon the 12 disk raid array )? On Thu, Jun 24, 2010 at 6:31 AM, Scott Marlowe <scott.marlowe@xxxxxxxxx> wrote: > 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
