I can fairly safely say that they work pretty darn well for mail spools. We use Netapps for most of our mail services, both for our national ISP service and some of our higher end systems, and other than some known issues with NFS3/TCP, we haven't had any specific locking-related problems.
And we're running many hundreds of thousands of mailboxes through this. Note, though, that we've rewritten all our delivery agents and POP3 software to do stronger locking than the standard distribution of sendmail or of various pop3 daemons. You'll definitely want to make sure that what you're using is robust enough to lock properly (for example, I've seen things that fopen, lock the fileno() of the stream, write to the stream, unlock the fd, and fclose...which can fail because the stream isn't flushed to the fd until the fclose).
--David Schairer Director, Core Technology Concentric Network Corp.
In our case, the client machines are SPARCs running Solaris 2.5.1
many of our readers are POP, rather than NFS; i would guess that no more than 50 machines actually NFS mount /var/spool/mail for any serious mail reading. our sole writer is Solaris 2.5, patched to the hilt.
Well I dunno. I deliever email to ~/.mailbox to ~200 users and automount everyone's directory from my 540 to an Ultra1. Been workin' like a champ for about nine months now. This Ultra also acts as a popper, users automount their home dirs too and use a wide variety of email readers.
I do, however, use procmail for local email delivery and use ".mailbox.lock" for locking. I haven't had an problems with this method except for Sun's mailtool which seems to sometimes randomly leave a ".mailbox.lock" . Solution seems to tell people "don't do that" *smirk* and instead use dtmail.
- mz
-- matthew zeier -- mrz@3com.com -- 3Com EWD Engineering -- 408/764-8420 ....................................................................... "Y el mundo se mueve, mas rapido y mejor." - Fey