On Mon, Dec 05, 2005 at 12:25:49PM +0100, Marten Lehmann wrote:

is dotlock supposed to work with NFS? I noticed that the default-locking method causes problems even with nfslockd started.

Dotlocking is the only sane locking mechanism over NFS. fcntl locks often work, too, depending on the clients and servers, but there are various corner cases where lockd (NFS's locking mechanism) fails... For instance, when a client, holding locks, goes offline. If the client (as identified by its ipaddress) stays offline, lockd is supposed to hold the locks forever. Whether your lockd does depends :P Dotlocks use NFS (not lockd) metadata semantics, and they work on all NFS combinations I've seen.

For small installations, or situations where a few stale lock files isn't that big a deal, fcntl locks are fine (if the servers and clients all co-operate.) If you want something that scales well or is less of a hassle in large installations, or if fcntl doesn't seem to work right, use dotlocking. Most importantly, though, make sure everything that locks the same file is using the same locking mechanism. So, if you use mbox mailboxes, and procmail to deliver to them, or pine to read them while dovecot may be reading them too, make sure they all lock the same way.

-- Thomas Wouters thomas@xs4all.net

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