[Dovecot] Best Cluster Storage

[Jan-Frode Myklebust]

On Thu, Jan 20, 2011 at 5:20 PM, Henrique Fernandes <sf.rique at gmail.com> wrote:

>> > Not all, if this counts as large:
>> >
>> >        Filesystem            Size  Used Avail Use% Mounted on
>> >        /dev/gpfsmail      9.9T  8.7T  1.2T  88% /maildirs
>> >
>> >        Filesystem            Inodes   IUsed   IFree IUse% Mounted on
>> >        /dev/gpfsmail     105279488 90286634 14992854   86% /maildirs
>> >
>>
>> how do you backup that data? :)
>>
> Same question!
>
> I have about 1TB used and it takes 22 hrs to backup maildirs!

Our maildirs are spread in subfolders under /maildirs/[a-z0-9], where
mail addresses starting with a is stored under /maildirs/a/, b in
/maildirs/b, etc.. and then we have distributed these top-level
directories about evenly for backup by each host. So the 7 servers all
run backups of different parts of the filesystem. The backups go to
Tivoli Storage Manager, with it´s default incremental forever policy,
so there´s not much data to back up. The problem is that it´s very
slow to traverse all the directories and compare against what was
already backed up. I believe we´re also using around 20-24 hours for
the daily incremental backups... so we soon will have to start looking
at alternative ways of doing it (or get rid of the non-dovecot
accesses to maildirs, which are probably stealing quite a bit
performance from the file scans).

One alternative is the "mmbackup"-utility, which is supposed to use a
much faster inode scan interface in GPFS:

http://publib.boulder.ibm.com/infocenter/clresctr/vxrx/index.jsp?topic=%2Fcom.ibm.cluster.gpfs31.basicadm.doc%2Fbl1adm_mmback.html

but last time we tested it it was a too fragile...


  -jf