[Dovecot] Maildir configuration vs ZFS and snapshots...

[Peter Eriksson]

>>     namespace private {
>>       separator = /
>>           prefix = snapshot/
>>           location = 
>> maildir:~/.zfs/snapshot/2007-06-18/Maildir:CONTROL=~/.dovecot/control:INDEX=~/.dovecot/index 
>>
>>     }
>>
...
> We are switching from the UW IMAP server with local disks to Dovecot 
> using a NetApp filer.  The filer provides snapshots too, although with a 
> slightly different layout as the ".snapshot" directory appears in each 
> and every directory with its files and folders.  For example:
> 
>     ~/Maildir/.snapshot/nightly.0/...
>     ~/Maildir/.snapshot/nightly.1/...
>     ~/Maildir/.snapshot/nightly.2/...
>         etc
> 
> where the ".0" suffixed directory is the most recent etc.

Uh.. I'n your case I think it would be quite easy. I think this should work:

   namespace private {
     separator = /
     prefix = snapshot-0/
     location = 
maildir:~/Maildir/.snapshot/nightly.0:CONTROL=~/.dovecot/control:INDEX=~/.dovecot/index 

   }
   namespace private {
     separator = /
     prefix = snapshot-1/
     location = 
maildir:~/Maildir/.snapshot/nightly.1:CONTROL=~/.dovecot/control:INDEX=~/.dovecot/index 

   }

etc... You won't see the INBOX either (like me) unless you create the
symlink suggested (.INBOX -> .) before taking the snapshots.

I think I tried setting up hierarchical namespaces but it didn't work
(I would have liked to see snapshot/0, snapshot/1 etc).


> In your example your snapshots seem to be in directories named after a 
> specific date (when the snapshot was taken?).  I was wondering if you 
> had some clever way of providing access to these; in your example above 
> you hard-code the names into the Dovecot configuration file, which 
> doesn't seem practical for a live system?

In ZFS you can name your snapshots anything you like, it's just a tag 
that you select when you create it like this:

    zfs snapshot -r andromeda/mail at 2007-07-04

(-r = take snapshot of all the subfilesystems too. Each user has their 
own filesystem here).

In a real live situation I'd probably name them "yesterday" "last-week" 
or something more suitable for the hardcoding in the dovecot.conf file. 
Our I'd look at creating some kind of dynamic internal namespaces 
(requires hacking of Dovecot :-).

I'd really like to be able to present all the available snapshots over 
IMAP if possible. However, I'm a bit worried though that the mail client 
will walk thru all the mailboxes in all the snapshots when accessing the 
server though...

> 
> Basically I'm trying to mimic your setup and was wondering if you had 
> already solved the problem of getting down from your "snapshot" 
> directory through the intermediate level to the Maildir itself.
> 
> In passing, would I need to use a separate CONTROL and INDEX storage 
> area for these, or will the files for the snapshot folders live happily 
> alongside those for the live area?  (I'm not too sure how the 
> organisation of these storage areas works when namespaces and prefixes 
> are concerned!)

You need to point the CONTROL and INDEX storage things outside of the 
readonly snapshots or Dovecot will complain when it wants to update the 
indexes...

- Peter