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...
