Using a SAN/GPFS with cyrus

[Ken Murchison]

Prentice Bisbal wrote:

> Ken, I'm not too familiar with QFS SANs. Does that have a filesystem 
> interfacewhere the filesystem itself allows multiple SAN clients to 
> access the same filesystem, etc?

Yes, its a shared filesystem.  Multiple clients can r/w simultaneously.

> What if the 2nd system was treated as a hot spare, and would't actually 
> do any mailserving functions until the primary server is shutdown. (ie 
> the switchover wouldn't be automatic - it would require human 
> intervention).

If you stop Cyrus on the primary, then start Cyrus on the spare, you 
should be OK.  The this case, you're essentially using the SAN as shared 
storage, not a shared filesystem (no different from physically moving 
the FC connection from one box to the other).


> Ken Murchison wrote:
> 
>> Prentice Bisbal wrote:
>>
>>> I'm installing Cyrus on a ssytem that will have access to an IBM 
>>> FAStT SAN with GPFS (a parallel filesystem allowing multiple servers 
>>> to share a filesystem on a SAN).
>>>
>>> For redundancy, I was thinking of creating the IMAP folder dir and 
>>> spool dir on the SAN and then having two mailservers setup 
>>> identically using cyrus. If the primary server  goes down for any 
>>> reason, the secondary would automatically begin receiving/delivering 
>>> mail based on the MX records in DNS.
>>>
>>> Would this present any problems with cyrus if two servers are 
>>> accessing the same directories/files? GPFS should manage file 
>>> sharing, but I'm wondering if there are any know problems with Cyrus 
>>> in this configuration.
>>>
>>> Has anyone done this before?
>>
>>
>>
>> Sharing mailboxes.db is prone to problems, if one machine trashes it, 
>> then the other machine(s) need to be halted while the db is 
>> reconstructed.  I'm involved in something similar using 3 or 4 load 
>> balanced Sun machines on a QFS SAN.  The current setup keeps separate 
>> mailboxes.db, deliver.db and tls_sessions.db on each machine (which 
>> means that duplicate delivery and Sieve aren't foolproof across 
>> machines).  I have modified imapd and mupdate to keep mailboxes.db in 
>> sync across the machines.  This code is currently being beta-tested, 
>> and I haven't heard any complaints for weeks.
>>
>> If you are interested in looking at this, checkout the unified-imapd 
>> branch from CVS.
>>
> 
> 


-- 
Kenneth Murchison     Oceana Matrix Ltd.
Software Engineer     21 Princeton Place
716-662-8973 x26      Orchard Park, NY 14127
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