[Box Backup] Two backup-servers

Chris Wilson boxbackup@fluffy.co.uk
Sun, 27 Jan 2008 16:10:18 +0000 (GMT)

Hi Markus,

On Sun, 27 Jan 2008, Markus Liljergren wrote:

> I'm trying to figure out the best way to deploy BoxBackup as a service 
> for my servers. All services provided by my servers have redundancy in
> the way that there is always another server ready to take over one or 
> more services in the event of one server failing to provide its assigned 
> services. When implementing BoxBackup in this setup I would like to have 
> all data stored on two different servers (with limited bandwidth between 
> them, for example NFS-based solutions would not work well).

It should be possible to synchronise the two servers with rsync. However 
rsync is not _that_ bandwidth-efficient or disk-efficient. You might 
consider running filesystems that support snapshots at both ends, and then 
locally computing the difference between two snapshots on the master and 
transferring just that difference to the slave. ZFS has built-in support 
for this (using the "zfs send" command).

> It would be preferable if the clients didn't have to backup to the two 
> servers separately.

I believe that someone here (I think it was Pete Jalajas) was running a 
similar setup and discovered that the bandwidth use between the two server 
sites (for synchronisation) was too high, so he found it better to run two 
completely independent backup configurations on each client.

> The question I have, is it possible to do it in this or a similar way 
> without risk of corruption due to incomplete syncs on server-failure? 
> Should I just abandon this and have the clients send backups to two 
> different servers?

I think that it is possible and that people are currently doing it.
I don't believe you have anything to worry about from a failed sync.

If you rsync from server A to server B while clients are backing up to 
server A, you will probably get some incomplete updates, lock files and 
inconsistent store statistics on B. You might want to run "bbstoreaccounts 
check fix" on each account on B after the transfer is complete.

If you do have any problems, please let us know. Good luck!

Cheers, Chris.
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