Re: Disk Mirroring

Mike Bristow (mike@shivan.demon.co.uk)
12 Sep 1996 22:32:50 GMT

In article <Pine.BSD.3.91.960912053226.22974F-100000@defender.lm.com>,
John_Wier <jbw@telerama.lm.com> writes:
>Can anyone tell me if there is a way of mirroring disks in Linux? We use
>this approach at work to give our system online redundance so if a disk
>starts to go bad, we break the mirror and take the offending disk/partitions
>off line until the repair/replacement is done. Since all data is
>duplicated on the mirror device, the user has no idea that a disk failure
>has occured.
>
You're after RAID support. Doesn't exist (yet). Very Clever People
are working on it...

For the cuurent state of play, look into md.

shivan:~> cat /usr/src/linux/Documentation/Changes
[...]
Multiple device
===============

Multiple device support (allowing you to group several partitions
into one logical device) has also been added. Check out
ftp://sweet-smoke.ufr-info-p7.ibp.fr/pub/Linux/md035.tar.gz to try this
out.

[...]

As I understand it, this is never as good as a special RAID controller.
<simplifcation>
This is a very clever box, which pretends to be a SCSI (or whatever) HDD
while actually containing 9 (or whatever) real SCSI HDD's. As far as Linux
is concerned, it's just got a SCSI HDD, and doesn't care any more.
</simplifcation>

These are normally better than a software solution, because you can do
things like take out a broken HDD, and replace it, while the system
is online.

They are, howvere, expensive....

Mike

-- 
The best UK M:tG tourney page: http://www.shivan.demon.co.uk/tourney/


(Not that I'm biased ;)