We will be deploying a replacement Dovecot server soon, and we are planning to use maildir for the primary storage, but with an archive namespace using mdbox (or perhaps sdbox), and SIS.

Our backup servers and (luke)warm spare server need to obtain full copies of the mail store. For the maildirs I know I can simply use rsync (we already use it here).

I'm a little wary of using rsync with mdbox and SIS though.

Obviously we would have to use the -H option of rsync to avoid duplicating the hard linked data, does anybody have any experience with how this scales? I've considered simply rsyncing the /var/mail/dovecot/attach/??/??/hashes folders. Is there a tool that can reconstruct the /var/mail/dovecot/attach/??/??/*-* links for a list of messages in that case?

I'm aware of "doveadm backup", and (although it currently throws up a few errors) it seems like it might be a valid solution for our warm spare server. Our backup servers, on the other hand, aren't supposed to be visible to the production machines, with the exception of the backup machine sshing in to do an rsync each night. We can't install dovecot on them.

To perform partial email recovery in maildir, we can simply log into a backup server, grep for emails of interest, and then scp them into a maildir new/ subfolder on the mail server to recover them.

What about using dbox? I can identify /var/mail/dovecot/archive/ash/dbox/storage/m.* files, and identify necessary attachments under /var/mail/dovecot/attach/??/??/ but once I've copied them over to the mail server is there a safe way to import them? Actually, converting to a maildir style file would be adequate if there is a script anywhere to do this. We'd still rather be backing up the deduplicated mailstore for obvious reasons.

Has anybody got any suggestions?

I'm aware of "dsync backup questions" ( https://www.dovecot.org/list/dovecot/2013-February/088070.html ) but there didn't really seem to be a solution.

Thanks,

Ash

PS Our current server has 257 users (though perhaps 100 are active), using around 225G in total.

PPS  Proposed new server configuration:

mail_location = maildir:~/Maildir:LAYOUT=fs
mail_attachment_dir = /var/mail/dovecot/attach
mail_attachment_fs = sis posix
mail_attachment_hash = %{sha1}
mail_attachment_min_size = 128 k

namespace _archive {
  list = yes
  location = mdbox:/var/mail/dovecot/archive/%n/dbox
  prefix = Archive/
  separator = /
  subscriptions = yes
  type = private
}

namespace _private {
  inbox = yes
  type = private
  separator = /
  subscriptions = yes
  prefix =
}