io performance...

[Max Waterman <davidmaxwaterman+kernel@fastmail.co.uk>]

Hi,

I've been referred to this list from the linux-raid list.

I've been playing with a RAID system, trying to obtain best bandwidth
from it.

I've noticed that I consistently get better (read) numbers from kernel 2.6.8
than from later kernels.

For example, I get 135MB/s on 2.6.8, but I typically get ~90MB/s on later
kernels.

I'm using this :

<http://www.sharcnet.ca/~hahn/iorate.c>

to measure the iorate. I'm using the debian distribution. The h/w is a MegaRAID
320-2. The array I'm measuring is a RAID0 of 4 Fujitsu Max3073NC 15Krpm drives.

The later kernels I've been using are :

2.6.12-1-686-smp
2.6.14-2-686-smp
2.6.15-1-686-smp

The kernel which gives us the best results is :

2.6.8-2-386

(note that it's not an smp kernel)

I'm testing on an otherwise idle system.

Any ideas to why this might be? Any other advice/help?

Thanks!

Max.