Hardware Striping

[Jens Schweikhardt]

Ken et al,

On Wed, Apr 21, 2004 at 03:02:10PM -0600, Kenneth D. Merry wrote:
# 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.

Yes, that's one of the reasons, plus certain issues with vinum.

# 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.

I also want to get rid of a lot of configuration and any possible
(present and future) maintenance issues that vinum and ccd have, like
GEOMification and End-Of-Life. I do not want to make any assumptions
about them, and the proper way to get rid of that issue is to simply not
use them. Call me paranoid :-)

# > 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.

I've looked at other Adaptec products, and found

 29320-R := single channel U320 RAID0,1   Part Number: 1978100

which appears close to what I want, namely not the fully fledged RAID>1,
and as a benefit there is an 68 pin Ultra Wide connector for my CD
writer and DVD reader, so all my present devices can be used with just
one controller.

The card is advertised with

   The Adaptec SCSI Card 29320-R is a half-size, 64-bit 133 MHz PCI-X,
   single-channel Ultra320 SCSI card with integrated HostRAID. The
   29320-R includes a legacy SCSI connector and is a cost effective
   hardware based RAID, a better alternative to software based RAID in
   the market today. It provides worry-free data protection at the
   fastest SCSI speeds available up to 320 MBps ideal for mainline
   storage, streaming video and audio, and other bandwidth-intensive
   applications. The card has a 68-pin HD external connector and a
   68-pin HD internal connector for Ultra320 SCSI (LVD) hard disks
   drives and a 68-pin/50-pin legacy SCSI connector. The 29320-R offers
   an unparalleled degree of investment protection and upgradability to
   Adaptec's entire SCSI RAID family of products.

It appears to have an "AIC-7901X" SCSI chip; would this card be
supported by the ahd driver? The man page just mentions AIC-7901 without "X".

Regards,

	Jens
-- 
Jens Schweikhardt http://www.schweikhardt.net/
SIGSIG -- signature too long (core dumped)