[3069] in SIPB-AFS-requests
Re: FY98 budgeting and AFS
daemon@ATHENA.MIT.EDU (Richard Basch)
Thu Jul 16 09:17:15 1998
Date: Thu, 16 Jul 1998 09:16:23 -0400
To: Bill Sommerfeld <sommerfeld@orchard.arlington.ma.us>
Cc: Greg Hudson <ghudson@MIT.EDU>, mhpower@MIT.EDU, sipb-machine-room@MIT.EDU,
sipb-afsreq@MIT.EDU
In-Reply-To: <199807152256.WAA13728@orchard.arlington.ma.us>
From: "Richard Basch" <basch@lehman.com>
On Wed, 15-July-1998, "Bill Sommerfeld" wrote to "Greg Hudson, mhpower@MIT.EDU, sipb-machine-room@MIT.EDU, sipb-afsreq@MIT.EDU" saying:
> I don't know anything about the Box Hill unit, but the one high-end
> RAID unit i'm familiar with (a Data General RAID unit remarketed by HP
> under a name I now forget) had dual-redundant everything, (including
> two control processors and two serial console ports), and a user
> interface for configuring `slices' of the RAID in various modes. (you
> could also configure it over the SCSI bus using SAM from HP-UX).
> there was much complexity.. it was a fun toy to play with when we were
> setting it up, which is not something I'd say about your joe average
> fast-wide SCSI drive..
Lehman employs dual-redundant RAID units... but it has been our
experience that there is still at least one or two components that are
not redundant. For instance, to have truly redundant control of the
RAID unit, you also have to install kernel extensions for path failover.
Also, the units themselves generally employ only one cache battery,
which needs to be replaced periodically... (sometimes the redundant
units don't rely on the cache, but their performance degrades when the
cache battery dies).
I believe that RAID units are more complex to manage than individual
disks -- for one, there is separate software for managing the RAID
disks, including the slices/groupings and the disk rebuilds (after a
failure). Unless you work with them frequently, the options can be
confusing.
As for reliability, we gave up on Boxhill at Lehman because of several
Boxhill support issues and RAID failures. At one time, Boxhill was the
leader in RAID support, but we do not feel this is the case anymore.
--
Richard Basch
AVP, Technology Integration URL: http://web.mit.edu/basch/www/home.html
Lehman Brothers, Inc. Email: basch@lehman.com, basch@mit.edu
101 Hudson St., 28th Floor Voice: +1 201 524 5049
Jersey City, NJ 07302-3988 Fax: +1 201 524 2111
