"jwatkins" == Jared Watkins <[EMAIL PROTECTED]> writes: jwatkins> I've not been able to find the answer to the GFS question jwatkins> in the archives.. so here goes. If one were using a dual jwatkins> attach scsi cabinet.. or fibre channel.. would it jwatkins> possible to use cyrus on GFS from two or more servers all jwatkins> with r/w access? I'm thinking of a setup that would have jwatkins> all user mailboxes visible to all cyrus servers.. but jwatkins> clients would be directed to different systems with jwatkins> perdition to balance the load. So if one server needed to jwatkins> come down.. you would simply take that system out of the jwatkins> pool and direct the users hitting it to the remaining jwatkins> cyrus servers.. increasing their load... but leaving the jwatkins> clients none the wiser. Jared
We were attempting to use IBM's GPFS to do exactly this. It isn't going to work well. The main problem is that Cyrus makes heavy usage of MMAP, and if you turn of MMAP in Cyrus, you've still got locking issues within BerkeleyDB. I posted a patch to this list a few weeks ago that get you about 85% of the way to using BerkleyDB's built-in RPC abstraction for the mailboxes.db, but it's just not going to work as well as Murder. There are also uses of MMAP within Cyrus that are looked on as unconventional. For example, Cyrus will MMAP a file (for r/w), then open the same file (from the same process) for writing -- thus invalidating the map. In a distributed filesystem, you've locked the mmap'd region of the file across the cluster -- that invalidation if *very* expensive. There will also be regular-old file locking issues. Since distributed filesystems are slow with meta-data updates, stat(), fcntl(), and friends are going to be painful. A Murder allows segmentation (for most purposes) of the mailboxes.db, which is the single-most-contended-for resource in Cyrus (as far as I can tell). The problem that *isn't* addresses is availability of each IMAP back-end. We're hoping to use IBM's HACMP for this, I think that there is a Linux-ish, scriptable-takeover-on-hearbeat-failure hooya, though I don't know what it is called. Can it be done? Yes. It won't give you even close to the same performance of a Murder. In our environment, it just sucked and we found out the hard way. Regards, -- Stephen L. Ulmer [EMAIL PROTECTED] Senior Systems Programmer http://www.ulmer.org/ Northeast Regional Data Center VOX: (352) 392-2061 University of Florida FAX: (352) 392-9440
