[Dovecot] Maildir messages

[Stan Hoeppner]

On 7/13/2012 7:28 AM, Wojciech Puchar wrote:
>>>
>>> not much difference.
>>
>> maildir requires 3 (or is it 4?) metadata operations and a file write op
>>
> your remarks are mostly true, except concentrates too much on uncommon
> situations and uncommon strange case of probably tens of thousands of
> mail accounts that must be very limited.

There are many folks on this list who ran out of IOPS due to maildir at
one time or another.  Nowhere near tens of thousands of accounts were
not required.  To solve the problem, they either purchased more
spindles, added RAID cache, or converted to mbox, or mdbox, depending on
when they ran into the problem (mdbox is very young).

> From my practice mail accounts are at least 1GB large, often 10GB. more
> often than not other user data is on the same disk.

Typical SMB setup it seems.

> i've never had more than 50 users on single disk set (which is always 2
> disks in mirror), And I/O was never ever a problem except first index
> build etc. in dovecot 2 you can do this in controller way using doveadm.
> 
> Mail I/O doesn't make that much part of I/O for me, still i found a bit
> speedup by moving dovecot indexes to SSD if it exist.

With only 50 users it's hard to saturate one disk with a mail workload.

> while disks get larger user data amount get larger too.
> 
> Today tape backups are hardly used because it is plain uneconomic today.

Tape is far more cost effective than a GbE MAN link to a hot site.

> most do backups by copying differences to other disk, preferably in
> other place.

Again, those links are usually more costly than off site tape rotation
services, and the backup window much larger.

> Adventages of pure Maildir format outweights everything else as you have
> one file -> one mail.

While that is maildir's greatest strength, it is also it's greatest
weakness.

-- 
Stan