Mirroring files over servers was Re: [OT]: bash or any other $favourite{shell}? [was: Wish list]

[Steve Mynott]

On Mon, Jun 12, 2006 at 03:01:51PM +0100, Dirk Koopman typed:

> I suppose what I am looking for is some kind of RAID 5 effort, but
> distributed across a few machines.

I evaluated DRBD for a customer who wanted mirrored servers about a year
back which was claimed to be network RAID-1 (mirror).

http://www.drbd.org/

It's not that easy to configure, but does work and but I particularly didn't
like the way the remote mirrored filesystem wasn't viewable in normal use (you
can't mount the remote node readonly), so you just had to trust that the
kernel module had done its work.  And I have to confess to a prejudice against
all networked file systems.  So I ended up doing it the old school way and
running rsync every 15 mins together with Mysql replication to the remote
server and local hardware RAID-5 disks, which seemed more risk adverse.

Actually one problem with the whole idea of mirroring is the possibility of
losing files on one disk and this file loss being synced over to the remote
(eg. if you are using rsync's dreaded --delete option).  

For this reason, and the possibility of rolling back changes, I now use
"rdiff-backup" and can recommend "backupninja" -- "a silent flower blossom
death strike to lost data".  However, you might be better off renaming that
one if presenting it as a solution to a PHB as "Enterprise Backup Solution
Pro" or similar.

SSHFS also looks interesting:

http://fuse.sourceforge.net/sshfs.html

-- 
Steve Mynott <steve at tightrope.demon.co.uk>