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 --PGP Public Key-- http://www.oceana.com/~ken/ksm.pgp
