[Dovecot] backup mdbox best strategy

Robert Schetterer rs at sys4.de
Sat Dec 7 11:04:02 EET 2013

Am 07.12.2013 08:53, schrieb Claus:
> Thanks for your suggestion to use maildir, but
> i'm sure the key problem are the large Number of small files.
> the backup goes first to diskstorage and afterwards to LTO4 Tapes.
> We backup with EMC-Networker. The backuptime of large files (some GB)
> are normal.
> I wonder if there is no one who operates a large Mailsystem with mdbox
> and has suggestions to backup this?

you are able to backup and restore mdbox with dsync ( never tested ),
but its not like with maildir simply i.e rsync the mailbox or one only mail
so you may find some combined strategy using both formats depending to
your kind of storage, as people said i wouldnt recommand backup to tape
in a direct way

why not simply do some testing with only one mdbox mailbox , should be
easy with dsync

> Claus
> Am 06.12.2013 11:51, schrieb Nick Edwards:
>> Claus,
>> Robert's suggestion is good, we backup maildir, with 5.9TB in 2 hours
>> to SATA , we also run a backup of that backup, so we have two extra
>> copies (this is on top of NAS snapshots)
>> tape is just too slow for anything serious these days.
>> N ik
>> On 12/5/13, Claus <claus.r at bayern-mail.de> wrote:
>>> Am 02.12.2013 20:37, schrieb Robert Schetterer:
>>>> Am 02.12.2013 18:47, schrieb Claus:
>>>>> Hello,
>>>>> i have to backup (tape library) a mailsystem with about 300.000
>>>>> Mailboxes on 2 backends. Summary of all mailboxes are 2 TByte.
>>>>> The mailstore is mdbox.
>>>>> Is it save to do a simple filesystem backup (full and incremental)
>>>>> with
>>>>> backupsoftware?
>>>> hm i wouldnt do that with mdbox, cause it does strongly depends to
>>>> index, but if you use dsync you could convert to maildir at backup,
>>>> maildir should be fine to store on tape, but with 2 TB this is only
>>>> good
>>>> for total desaster archive, i guess it would take long time to restore
>>>> specially single mailboxes in acceptable time, from tape
>>>> Better use cheap sata storage raids for frequent backups, and do tape
>>>> snapshots sometimes.
>>>>> What is the prefered strategy to do a backup for desaster recovery
>>>>> (mailsystem crash) and restoring single usermailboxes?
>>>> dsync should do fine
>>>> http://wiki2.dovecot.org/Tools/Dsync
>>>> but there is no universal answer to this, perhaps filesystem snapshots
>>>> strategy might better, it depened on your general setup , filesystems ,
>>>> mailstore etc.
>>>> wait for others report their solutions, and find the one fits best at
>>>> your place
>>>>> Regards,
>>>>> Claus
>>>> Best Regards
>>>> MfG Robert Schetterer
>>> thanks for your answer,
>>> the main reason we plan to use mdbox is to reduce backuptime.
>>> Now we are using Maildir on cyrus and the (full)-backup takes about 20
>>> hours on one backend storing 150 GB of Mails in about 3 million files.
>>> Because of that we have many backends, so we can parallelize the backup
>>> prozess.
>>> greets, Claus

Best Regards
MfG Robert Schetterer

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