Server failover

[Matt Graham]

From: keith smith <klsmith2020 at yahoo.com>
> I am looking for information on how I might be able to mirror one
> server onto another and set them up so if the main server dies
> the second server will take over automatically.

heartbeat and drbd.  http://linux-ha.org/ and http://drbd.org/ to
start.
 
> The mirroring would require the website content itself and the
> MySql data.

drbd works below the filesystem level, if you want to use that.  You
really need a dedicated high-speed link between the 2 systems if you
want to use drbd.  Unless you use one of the newer and less well
tested filesystems such as GFS, if you use drbd, you have to have the
primary machine mount the filesystem, and the secondary machine can't
mount the filesystem at all.  Scripts allow the secondary machine to
become primary if/when the primary flails over.
 
> Now if I had 3 servers would I be able to do this by having them
> all three working as a "farm" to serve up multiple websites?

Not in the way described above.  drbd is very much a 2-machine system.
You could have a drbd cluster with large disks acting as the main
fileserver, and 1..N machines that mount the filesystems on that
server via NFS.  Then machines 1..N could serve content via apache
or apache combined with ldirectord.
 
> Is it possible to do this on a small budget?

Define "small".  You need boxes, time to set it all up, and disks.

-- 
Matt G / Dances With Crows
The Crow202 Blog:  http://crow202.org/wordpress/
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