[Dovecot] Dovecot + DRBD/GFS mailstore

[Mario Antonio]

Eric,

Thanks for the update ...

How does the system behave when you shutdown one server, and bring it 
back later ?  (are you using an IP load balancer/heart beat etc ?)

Regards,

Mario Antonio


Eric Jon Rostetter wrote:
>
> To update an old thread...
>
>>> I'm looking at the possibility of running a pair of servers with
>>> Dovecot LDA/imap/pop3 using internal drives with DRBD and GFS (or
>>> other clustered FS) for the mail storage and ext3 for the root drive.
>
>> I'm in testing right now with this setup.  Two Dell PE 2900 servers
>> (quad core @ 2.3 GHz, 8 GB RAM, raid 10 for the GFS+DRBD disk, raid 1
>> for the ext3 disks).  Running DRBD as a master/master setup.
> [...]
>> So far it is early testing.  63 users, but only about 12 of those are
>> "power users".  The performance has been real good so far, but as I say,
>> not many users yet.
>
> Well, as of yesterday, I've gone "live" with this setup with about 1K 
> users.
> Averaging about 150 to 200 concurrent sessions (higher during certain
> day hours, lower at night, etc).
>
> Slightly slower with 1K users than with 63 users (of course) but so
> far it is proving very stable and reasonably fast.
>
> Most of the time it is performing faster than my old system with 
> similar load,
> though there are rare "stalls" of webmail imap operations (connect, 
> get data,
> and disconnect session) where it might take about 5 to 10 seconds to 
> complete.
> I'm thinking it is a locking issue, but not sure.  The average time 
> for such
> a webmail operation is 0 to 2 seconds (which is reasonable, based on the
> message/mailbox size; using mbox here, so we have some 2 GB to 3 GB mbox
> files with large messages in them, etc).
>
> Anyway, the point is that doing a cluster like this is very reasonable
> from a cluster/stability point of view.  Jury is still out on 
> performance,
> but I should know soon since I've now got a "significant" number of users
> hitting it.
>
> My gut feeling is that there will be some slow connections from time to
> time due to locking probably, but that overall it will scale under load
> better and not die when a spammer attacks us or we otherwise get 
> flooded...
>