Hardware Striping

[Kenneth D. Merry]

On Wed, Apr 21, 2004 at 22:44:09 +0200, Jens Schweikhardt wrote:
> hello, world\n
> 
> I want to change my system to no longer use vinum for striping, but
> rather a hardware solution. I do not intend to use mirroring or any
> other RAIDn>0 functionality. I have two pairs of identical U160 SCSI
> disks (2 Fujitsu MAN and MAM with 36GB each) where I want to build two
> mirrors, one from the MANs, and one from the MAMs. You get the idea.
> 
> Until now I'm using an Adaptec 29160 Host Adapter, but of course it is
> not HW-RAID0 capable. What card am I looking for?

The only reason to go with a hardware controller for RAID-0 is if you want
to boot from the array.

Otherwise, you'll get better performance by using a software RAID-0
solution.  Going through a RAID stack and a SCSI layer on a RAID card with
a comparatively slow processor will generally be slower than using your
much faster host processor to do all of that.

ccd is an alternative if you don't want to use vinum.

> The disks have a sustained read rate of 60 to 70 Mbyte/s, so if all of
> them were used at the same time they could saturate an U160 bus. Is this
> a problem?

It's not a problem, unless you're interested in performance.  I'd suggest a
2 channel Ultra160 or Ultra320 RAID controller.  Hopefully the processor on
the RAID controller will be able to keep up with the 280MB/sec theoretical
maximum bandwidth from those disks.

As for alternatives, you could get an Adaptec 2200S, or an LSI MegaRAID
SCSI 320-2.  I think the driver for the Adaptec is probably a little better
maintained at the moment.  I haven't used either card, though, so I can't
really comment on them more than to point out the alternatives.

Ken
-- 
Kenneth Merry
ken at kdm.org