RAID-1 as back-up

[Karl Denninger]

On Sat, Jun 04, 2005 at 12:26:20AM +0200, Hans F. Nordhaug wrote:
> Dear list,
> 
> I would like to use RAID-1 as a back-up solution. If one of the disk
> breaks I would like my server to continue to run from the other disk.
> I have followed the mailing list for a while and read some howtos,
> but I'm not sure if this is possible (without doing all kinds of tricks
> when the accidents happens - removing meta data and so on). In
> addition, I thought, gvinum was the way to go, but hasn't there been
> some problems with it (reported here lately)? I'm running 5.3 - what
> do you recommend - gvinum, ccd, others? What is the definitive howto for
> the recommend solution. Thx for your time.
> 
> Regards,
> Hans

I do this using gmirror; I run a two-disk Raid1 system for normal operaton,
and back up to a third device which a CRON job attaches and detaches nightly
to image the system.

The detached disk is removed, so it will not be detected as a valid device
on boot.  If the online mirror breaks (either disk) the other continues on
its merry way.

In a catastrophe where the system scribbles on BOTH disks, the other volume
can be booted manually and with a bit of effort (couple of command-line
entries from single user mode) brought online as a single device.

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