[Dovecot] Highly Performance and Availability
Wayne Thursby
wayne.thursby at pgllc.com
Tue Feb 16 07:42:57 EET 2010
Hello everyone,
I am currently running Dovecot as a high performance solution to a particular
kind of problem. My userbase is small, but it murders email servers. The volume
is moderate, but message retention requirements are stringent, to put it nicely.
Many users receive a high volume of email traffic, but want to keep every
message, and *search* them. This produces mail accounts up to 14+GiB. After
seeing the failures of my predecessors, I transitioned to Postfix/Dovecot and
haven't looked back. Things are running nicely with the below setup.
Postfix and Dovecot running on the same virtual machine on a Dell 2950
with 1x Xeon E5440 on ESXi 4. Maildirs served up by 10x146GB 15k RPM SAS drives
on RAID-10 via direct attached Dell MD-1000.
We are transitioning other services to high availability, and I'm wondering
exactly how to provide some kind of near-realtime failover for my
Postfix/Dovecot machine. The MD-1000 provides nothing in the way of iSCSI, but
it *does* have two SAS connections available, only one of which is in use.
I have been looking at the Dell EqualLogic stuff and it seems to provide what we
need. I can get most of the information I need from the rep, but I wonder if
anyone has any experience with high performance requirements on these kinds of
storage.
I'd like to continue running my current hardware as the primary mail server, but
provide some kind of failover using the SAN. The primary usage of the SAN will
be to make our 2TB document store highly available. I'm wondering what kind of
options I might have in the way of piggybacking some email failover on this kind
of hardware without sacrificing the performance I'm currently enjoying.
Is it possible to go with a virtual machine mounted on iSCSI acting as a backup
mail server? How would I sync the two, NBD+MD? Any experience doing this with
maildirs? I wonder about the performance.
Can it be as simple as attaching my MD-1000's second controller to the SAN magic
box via SAS and pressing the Easy button?
Is it as expensive as running my primary mailserver mounted from the SAN via
Fiber Channel? Will that get me under 30ms latency?
I welcome any suggestions the group may have.
--
Wayne Thursby
System Administrator
Physicians Group, LLC
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