[Dovecot] Compressing existing maildirs

[Stan Hoeppner]

On 12/30/2011 8:41 AM, Jan-Frode Myklebust wrote:
> On Thu, Dec 29, 2011 at 07:00:03AM -0600, Stan Hoeppner wrote:
>>> We just got rid of the legacy app that worked directly against the
>>> maildirs, which is the reason we now can turn on compression. I
>>> intend to switch to mdbox, but first I need to free up some disks by
>>> compressing the existing maildirs (12 TB maildirs, should probably
>>> compress down to less than half).
>>
>> How much additional space do you expect the conversion process to
>> compressed mdbox to consume?
> 
> Somewhere around 1/3 of the current usage, I expect..
> 
>> It shouldn't need much.  Using dsync, the
>> conversion will be done one mailbox at a time and the existing emails
>> will be compressed when written into the new mdbox mailbox.
> 
> Yes, I know, but I intend to do more than just convert to mdbox. I want
> to fix the whole folder structure*, in a new filesystem with different
> settings (turn on metadata-replication, and possibly also data
> replication). So I need to free up some disks before this can start.
> 
> [*] move away from @Mails /atmail/a/b/abuser at domain folder structure to
> mdbox:/srv/mailbackup/%256Hu/%d/%n, stop having home=inbox, 
> possibly use many smaller fs's instead of one huge, move the indexes
> inside home...

Roger that.  Good strategy.  You using SAN storage or local RAID?  What
filesystem do you plan to use for the new mailbox location?  What OS is
the Dovecot host?  Lastly, how many users you have?  Sorry for prying,
I'm always really curious about system details when someone states they
have 12TB of mailbox data. ;)

-- 
Stan