Question: Disk Mirroring preceding RAID?

From: Clint Wolff <>
Date: Mon Dec 4 21:49:13 2000

On Mon, 4 Dec 2000, Stan Sieler wrote:

> 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.)

The term "disk mirroring" predates the term "RAID 1". The authors of
the RAID paper (students IIRC) just assigned a standard name to it.

> 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".)

Hmmm. I think RAID 1 is defined at a high enough level to encompass
all mirror techniques (hardware and software). IE RAID 1 is
maintaining an exact copy of the data on two (or more?) drives.

> 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
Received on Mon Dec 04 2000 - 21:49:13 GMT

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