On Tue, 6 Nov 2007, Dimitri Fontaine wrote:
Some knowing-better-than-me people on #postgresql had the remark that depending on the write transaction volumes (40 to 60 percent of my tps, but no so much for this hardware), I could somewhat benefit in setting the WAL on the OS raid1, and having 8 raid10 disks for data
That really depends on the write volume to the OS drive. If there's lots of writes there for things like logs and temporary files, the disruption to the WAL writes could be a problem. Part of the benefit of having a separate WAL disk is that the drive never has to seek somewhere to write anything else.
Now, if instead you considered putting the WAL onto the database disks and adding more disks to the array, that might work well. You'd also be losing something because the WAL writes may have to wait behind seeks elsewhere. But once you have enough disks in an array to spread all the load over that itself may improve write throughput enough to still be a net improvement.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
