On Wed, 2006-11-22 at 11:02, Jeff Frost wrote: > On Wed, 22 Nov 2006, Joshua D. Drake wrote: > > >> I could only find the 6 disk RAID5 numbers in the archives that were run with > >> bonnie++1.03. Have you run the RAID10 tests since? Did you settle on 6 disk > >> RAID5 or 2xRAID1 + 4XRAID10? > > > > Why not 6 drive raid 10? IIRC you need 4 to start RAID 10 but only pairs > > after that. > > A valid question. Does the caching raid controller negate the desire to > separate pg_xlog from PGDATA? I remember seeing something on the list a while back that having separate file systems was as important as having separate disks / arrays for pg_xlog and PGDATA. Something about the linux on the machine under test being better at ordering of writes if they were to two separate file systems. Of course, the weird thing is how counter intuitive that is, knowing that the heads will have to move from one partition to another on a single disk. but on a multi-disk RAID10, it starts to make sense that the writes to pg_xlog and the writes to data would likely be happening to different drives at once, and so having them be on separate file systems would make it faster if the kernel was better at handling the ordering that way. It's worth looking into at least. Oh, and another vote of confidence for the LSI based controllers. I've had good luck with both the "genuine" article from LSI and the Dell aftermarket ones. Avoid the Dell - Adaptec controllers like the plague. If you're lucky being slow is the only problem you'll have with those. I'm really hoping to spec out a data warehouse machine here in the next year with lots of drives and an Areca or LSI controller in it... This thread (and all the ones that have come before it) has been most useful and will be archived.
