[Dovecot] SSD drives are really fast running Dovecot

[Brad Davidson]

>> The reason is that few if any organizations actually need
> 28TB (14
>> 2TB Cavier Green drives--popular with idiots today) of mail storage
in a
> single
>> mail store.  That's 50 years worth of mail storage for a 50,000
employee
>> company, assuming your employees aren't allowed porn/video
attachments,
> which
>> which most aren't.
>>
> 
> WTF?  28TB of mail storage for some is rather small. Good to see your
> still posting without a clue Stanley.
> Remember there is a bigger world out there from your tiny SOHO

I'm with you Noel.

We just bought 252TB of raw disk for about 5k users. Given, this is
going in to Exchange on Netapp with multi-site database replication, so
this cooks down to about 53TB of usable space with room for recovery
databases, defragmentation, archives, etc, but still... 28TB is not much
anymore.

Of course, Exchange has also gone in a different direction than folks
have been indicating. 2010 has some pretty high memory requirements, but
the actual IOPS demands are quite low compared to earlier versions.
We're using 1TB 7200RPM SATA drives, and at the number of spindles we've
got, combined with the cache in the controllers, expect to have quite a
good bit of excess IOPS.

Even on the Dovecot side though - if you use the Director to group your
users properly, and equip the systems with enough memory, disk should
not be a bottleneck if you do anything reasonably intelligent. We
support 12k concurrent IMAP users at ~.75 IOPS/user/sec. POP3, SMTP, and
shell access on top of that is negligible.

I'm also surprised by the number of people trying to use DRBD to make
local disk look like a SAN so they can turn around and put a cluster
filesystem on it - with all those complex moving parts, how do you
diagnose poor performance? Who is going to be able to support it if you
get hit by a bus? Seems like folks would be better off building or
buying a sturdy NFS server. Heck, even at larger budgets, if you're
probably just going to end up with something that's essentially a
clustered NFS server with a SAN behind it.

-Brad