Backups and disaster recovery

[Sam Kuper]

On Sat, Dec 03, 2022 at 11:02:54PM +0000, GDS wrote:
> Hello all! After reading some of the past threads on backups, I was
> wondering if I could get a sanity check... I run a Maildir
> configuration for a small (10 mailboxes) mail server. Using "doveadm
> backup", for each mailbox I do:
>
> - Weekly full backups and then copy the files to a network-based
> filesystem.
>
> - Daily incremental backups and then copy the files to a
> network-based filesystem.
>
> My recovery assumption is that in case of hardware failure, I would
> re-set up the mail service and for each mailbox I will recover at the
> right directory the latest full mailbox backup and on top of it, each
> incremental backup to the latest day.  Does this sound like a sound
> strategy?

Assumptions are dangerous things.

Have you tested your assumptions - i.e. simulated recovering from a
hardware failure - in order to be sure your backups and procedures are
adequate?

Are your server, and your network-based filesystem protected against
bit-rot?


> Also, I was thinking of setting up a second dovecot server on another
> server and replicating my primary on an hourly basis to decrease
> recovery time.  But I looked at mbsync and it seems to require mailbox
> login/password for each mailbox (which I don't have). Is there an
> alternative?

You might want to consider using ZFS.

https://en.wikipedia.org/wiki/ZFS

https://openzfs.org

Jim Salter has written some fairly accessible tutorials.  For instance:

https://arstechnica.com/information-technology/2014/02/ars-walkthrough-using-the-zfs-next-gen-filesystem-on-linux/3/

https://arstechnica.com/information-technology/2015/12/rsync-net-zfs-replication-to-the-cloud-is-finally-here-and-its-fast/

https://arstechnica.com/information-technology/2020/05/zfs-101-understanding-zfs-storage-and-performance/

https://jrs-s.net/category/open-source/zfs/

Sam