Re: how to partition disks

hubert depesz lubaczewski writes:

> On 6/14/06, Sven Geisler
> raid 10 is of course not questionable. but are you sure that it will work
> faster than for example:
> 2 discs (raid 1) for xlog
> 6 discs (raid 10) for tables
> 6 discs (raid 10) for indices?

Caching up on the performance list.
Although this may not help the original poster.. wanted to share a recent
experience related to allocation of disks on a raid.

We just got a server with 16 disks.
We condfigured 12 to 1 raid controller and a second raid with 4. Both using
raid 10.

RAID 1
10 x 7,200rpm disks
2 hot spares

RAID 2
4 x 10,000 rpm disk

One of the things I always do with new machines is to run bonnie++ and get
some numbers.

I expected the second raid to have better numbers than the first because the
disks were 10K drives (all SATA). To my surprise the larger raid had better
numbers.

So I figure the number of spindles on a single RAID does make a big
difference. To that regard splitting 16 disks into 3 sets may help with data
needing to be read/written to be in separate raids, but may degrade
performance by reducing the number of spindles on each of the raids.