On Wed, Aug 09, 2006 at 10:15:27AM -0500, Scott Marlowe wrote: > Actually, the BIGGEST win comes when you've got battery backed cache on > your RAID controller. In fact, I'd spend money on a separate RAID > controller for xlog with its own cache hitting a simple mirror set > before I'd spring for more drives on pg_xlog. The battery backed cache > on the pg_xlog likely wouldn't need to be big, just there and set to > write-back. > > Then put all the rest of your cash into disks on a big RAID 10 config, > and as big of a battery backed cache as you can afford for it and memory > for the machine. Actually, my (limited) testing has show than on a good battery-backed controller, there's no penalty to leaving pg_xlog in with the rest of PGDATA. This means that the OP could pile all 8 drives into a RAID10, which would almost certainly do better than 6+2. Note that some controllers (such as 3ware) need to periodically test the life of the BBU, and they disable write caching when they do so, which would tank performance. -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
