[Dovecot] Please help to make decision

[Stan Hoeppner]

> On 25/03/2013 18:47, Thierry de Montaudry wrote:

>> This is just my experience, it might not be the best, but with the
>> (limited) budget we had, we finally came up with a solutions that can
>> handle the load and got us away from SAN systems which could never
>> handle the IOs for mail access. Just for the sake of it, our storage
>> machines only have each 4 x 1T SATA drives in RAID 10, and 16G of mem,
>> which I've been told would never do the job, but it just works. Thanks
>> Timo.

With only 48 effective 7.2k data spindles and 1M users, this would tend
to suggest that only a tiny fraction of your users are logged in and
performing IOs at any point in time.

Number of active sessions dictates IOPS requirements, not total
#mailboxes, and the former may be drastically different between these
two 1M user sites.  If 500K of your 1M users were logged in concurrently
via webmail I'd guess the heads of those 96 drives would hit their peak
seek rate instantly and remain there, and iowait would go through the roof.

My previous posts in this thread make the assumption that the worst case
scenario to architect for is 500K logged in active IMAP users at a given
PIT.

-- 
Stan