Using a SAN/GPFS with cyrus
ken at oceana.com
Wed Jan 21 14:16:42 EST 2004
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
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
--PGP Public Key-- http://www.oceana.com/~ken/ksm.pgp
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