[Dovecot] SIS and restoring from backups

[Charles Marcus]

On 2012-03-24 8:08 AM, Timo Sirainen <tss at iki.fi> wrote:
> You can do full backups from a filesystem snapshot, which works
> "well enough" (might leave some unused attachments lying around in
> some rare cases, but that can also happen if Dovecot crashes/dies).

But the problem isn't with backups, but with restores, right?

> The other possibility is to already use dsync (doveadm backup) to do
> full backups. With the redesigned dsync you would be able to do
> incremental backups also. In any case the solution involves
> de-SISing mails for backup.

So, this would make the backup storage requirements larger - maybe 
dramatically larger for sites that have a lot of large attachments?

Doesn't sound ideal...

I currently use rsnapshot to keep many multiple (daily, weekly, and 
monthly) hardlinked snapshots, each of which consumes only a tiny 
fraction of extra storage over and above the first/main snapshot.

Am I correct that enabling SIS as it is currently implemented would 
break this backup tool?

I was also thinking of asking about how to provide read-only access to 
these backup snapshots to the users in some kind of special namespace, 
so that they could all essentially go 'back in time' to grab any emails 
that they may have inadvertently deleted...

-- 

Best regards,

Charles