Question: Disk Mirroring preceding RAID?

From: Richard Erlacher <edick_at_idcomm.com>
Date: Mon Dec 4 19:07:17 2000

Back in '90. I tried the Novell NETWARE approach to mirroring, but was
unable to make it work. That was due to the fact that the ADAPTEC
controller I was using didn't really work correctly at the alternate address
with the driver they provided for that purpose. I quickly abandoned it, in
favor of the software RAID offered by NT.

It's theoretically quite solid, but I've never used it myself. The NT
(software) approach seems more solid. RAID is always done in software to
greater or lesser extent. The RISC processors commonly used on
"RAID-5-capable" controllers is really the same thing as it really doesn't
matter who runs the software. Unfortunately, under NT4, there were problems
with inter-process communication before SP3. That would make anybody
suspicious. My NT server was emulating the NETWARE server, yet had the
advantage of the software compression offered by NT and the built-in backup
(not the best imaginable, but the best there is <sigh>) AND it emulates the
NETWARE server so I can use it from DOS workstations.

regards,

Dick

----- Original Message -----
From: "Stan Sieler" <ss_at_allegro.com>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, December 04, 2000 11:53 AM
Subject: Question: Disk Mirroring preceding RAID?


> Hi,
>
> Need help in settling argument...does disk mirroring (via hardware)
> predate RAID's mirroring capability? (I'm not interested in
> OS software implemented mirroring here.)
>
> Also, are there any hardware mirror methods that one could point
> to and say: this is not capable of being called any kind of RAID!
> (The argument in question is over the statement that
> "all hardware based mirroring is a form of RAID".)
>
> For example, is there any "stealth hardware mirroring" mechanism,
> where a drive watches the bus, and obeys writes, but nothing else?
> (This would be "drive-based" mirroring, as opposed to "controller-
> based mirroring") (Since RAID is controller-based, a drive-based
> mirroring mechanism would seem to be clearly not any kind of RAID.)
>
> thanks!
>
> Stan
>
> Stan Sieler sieler_at_allegro.com
> www.allegro.com/sieler/wanted/index.html www.allegro.com/sieler
>
>
Received on Mon Dec 04 2000 - 19:07:17 GMT