High availability email server...

[David Korpiewski]

I spent about 6 months fighting with Apple XSAN and Apple OSX mail to 
try to create a redundant cyrus mail cluster.  First of all, don't try 
it, it is a waste of time.  Apple states that mail on an XSAN is not 
supported.  The reason is that it simply won't run.   The Xsan can't 
handle the large amount of small files and will do things like 
disconnect or corrupting the file system.

So my suggestion is to make sure that your san can handle the large 
amount of files that a mail server will be reading and dumping.  The 
Xsan had severe problems to the point of file system corruption while 
trying to deal with them, so make sure your san can handle it.

Our final solution which we are still in the process of finishing is to 
create a linux cluster with two servers each with their own XRAID 
backend.   Using replication, we mirror one server to the other.  Using 
some sophisticated software we wrote, we can validate the mailstore ages 
and then create a fully see-sawable cluster system.

Good luck!
David



Chris St. Pierre wrote:
> Chad--
> 
> We've put /var/lib/imap and /var/spool/imap on a SAN and have two
> machines -- one active, and one hot backup.  If the active server
> fails, the other mounts the storage and takes over.  This is not yet
> in production, but it's a pretty simple setup and can be done without
> running any bleeding edge software, and it appears that it will work
> fine.  There's no need to use a SAN, either -- you could share your
> mail storage out via NFS with the same effect.
> 
> We're going production with this in mid-August; if you'd like to know
> how everything goes, drop me a note in a month or so.
> 
> Chris St. Pierre
> Unix Systems Administrator
> Nebraska Wesleyan University
> 
> On Thu, 27 Jul 2006, Chad A. Prey wrote:
> 
>> OK...I'm searching for strategies to have a "realtime" email backup in
>> the event of backend failure. We've been running cyrus-imap for about a
>> year and a half with incredible success. Our failures have all been due
>> to using junky storage.
>>
>> One idea is to have a continuous rsync of the cyrus /var/spool/imap
>> and /var/lib/imap to another server
>>
>> I've also considered delivering email to two discreet email backends and
>> keeping the /var/lib/imap file sync'd . I don't think I can use murder
>> to do this.
>>
>> Is anyone out there using RHEL in a cluster that would like to share
>> their architecture? Any contractors out there that want to get paid to
>> help us implement?
>>
>> Chad P.
>> cprey at salk.edu
>> Salk Institute for Biological Studies
>>
>>
>> -- 
>>
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-- 
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David Korpiewski                     Phone: 413-545-4319
Software Specialist I                Fax:   413-577-2285
Department of Computer Science       ICQ:   7565766
University of Massachusetts Amherst
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