tech-kern archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: Scsipi guru needed...

On Sun, 30 Nov 2008, Anders Magnusson wrote:

I have been trying to find out why the performance of the ciss controller (Compaq raid) in
DL38x is really bad, but as I don't understand anything about the scsipi
layer (are there any docs?) I must ask around.  All this is really strange.

Writing data to the raw sd device (bs=64k) gets just over 7MB/s, which is quite slow.
Some debugging showed that:
- A write transfer (from given to the ctlr to interrupt) takes 8ms. Ok, no write cache on the ctlr maybe?

  Does your controller have a battery backup?  I've found that without the
battery backup, the controller does not use any write cache and write speeds are significantly reduced.

Michael L. Hitch              
Computer Consultant
Information Technology Center
Montana State University        Bozeman, MT     USA

Home | Main Index | Thread Index | Old Index