Date: Tue, 05 Apr 2011 01:01:23 -0700 From: perryh@pluto.rain.com To: cswiger@mac.com Cc: scrappy@hub.org, freebsd-net@freebsd.org, rmacklem@uoguelph.ca Subject: Re: 7-STABLE NFS: fatal: "select lock: Permission denied" Message-ID: <4d9acc53.w52H7UX61%2B6sZ3rH%perryh@pluto.rain.com> In-Reply-To: <AB2EA7D5-2EBF-44E2-BEC6-DDFB0772F5C2@mac.com> References: <1359778820.2757108.1301963093210.JavaMail.root@erie.cs.uoguelph.ca> <AB2EA7D5-2EBF-44E2-BEC6-DDFB0772F5C2@mac.com>
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Chuck Swiger <cswiger@mac.com> wrote: > It's fairly common to scale up a mail infrastructure from one box > handling both SMTP and IMAP (or POP) to a SMTP-only box writing to > NFS-mounted user mailboxes, and have one or more dedicated reader > boxes which only run IMAP/POP daemons which access that same NFS > filesystem holding the user mailboxes. Yikes! The _proper_ way to scale up from one box to multiple goes something like this: SMTP Internet ---> mail.<domain> [original box] This box now runs only the SMTP receiver, and perhaps the spam/virus filtering (if it has enough capacity). It contains no user mailboxes. SMTP mail.<domain> --+--> mailbox01.<domain> | This box runs local delivery, and IMAP/POP | daemons, for some user mailboxes (which are | stored on _local_ disks). It may also handle | spam/virus filtering for those mailboxes, if | mail.<domain> can't handle that load. | +--> mailbox02.<domain> | This box is just like mailbox01, for a different | set of user mailboxes. | +--> mailbox03.<domain> etc. -- as many as needed. mail.<domain> becomes a multiplexer, so that the outside world can send to <user>@mail.<domain> (or simply <user>@<domain> if you prefer) without needing to know about the internal structure. The multiplexing can be very simple, and thus very fast, by doing a table-lookup based on the first character of <user>. There's no need for NFS anywhere in the setup. > ... I've been burned by NFS locking (mis)adventures in the past, > and I hate to see people depend on it if they have alternatives.... As have I. Once. That was enough.
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