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Re: K8S Pro (S2882UG3NR) + Sil 3114 (Raid 1) + Sarge

On Tue, 2004-10-26 at 23:28 -0400, Lennart Sorensen wrote:
> On Sun, Oct 24, 2004 at 08:28:35PM -0500, Ron Johnson wrote:
> > Isn't *all* real h/w RAID "just secret proprietary software" on
> > the RAID controller?  Whether it be in flash or an EEPROM, real 
> > h/w RAID controllers have a dedicated (usually specialized) CPU
> > for handling the RAID calculations, SCSI commands, RAM cache, etc.
> > 
> > Thats why when you call up IBM, HP or Sun with a disk-related issue,
> > they ask you if your SCSI cards & RAID controllers are at the latest
> > ROM version.
> Well software raid is defined as raid that does the calculations in
> software (on your cpu), while hardware raid does the calculations using
> custom circuitry or a dedicated cpu running some software (firmware).
> If I have to waste cpu time on raid, I at least want to be able to see
> the code running on my cpu and perhaps be able to improve on it.  That
> is the difference.

Ummm, but with true h/w RAID, you are *not* wasting main CPU time
on it.  On "enterprise systems", the SCSI card itself doesn't even 
know that it's talking to a RAID set, since the SCSI cards connect
to a "RAID controller", which the SCSI disks also plug into.

A good example of this is/was the DEC/Compaq HSZ controllers.
These are 1-Up rack-mounted computers dedicated only to managing
SCSI disks in RAID configurations.  512MB battery-backed RAM, the
ability to join with another controller in a dual-redundant mode
(so that you had an effective 1GB of cache).  I don't know how 
things worked in Digital Unix, but under VMS, you connect to it
via SET HOST/HSZ to configure it.  You could also plug a VT-220
terminal directly into it.  Very convenient for initial configur-

Oh, and it worked with shared-disk VMS clustering.

Ron Johnson, Jr.
Jefferson, LA USA
PGP Key ID 8834C06B

"Never for the sake of peace and quiet deny your convictions."
Dag Hammarskjold

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