On Sat, 6 Sep 1997, David W. Tamkin wrote:
Edward Marshall wrote,
| a) Procmail still locks everything in sight. This is a performance hit,
| but it won't hurt anything, and the performance hit has always been
| there anyway. Low priority.
Surely that can be cured by compiling procmail with no kernel-locking
strategies enabled.
Not in this particular case; what's really desirable for maildir is to not
lock anything, but for anything else, employ the proper locking strategies
(i.e. flocking on mbox-format mailboxes).
| Shouldn't the world really be using Maildir anyway?
That depends: just what is Maildir (I know what procmail's MAILDIR variable
is, of course) and where does one find out more?
I should have explained a bit in my post to the procmail list; Maildir is
a mail storage mechanism made popular by qmail, which has the feature of
providing reliable delivery of messages, even over NFS, without needing
locks.
Unlike mbox format, maildir stores each message in a uniquely named file
based on time, process id, and machine name. It handles locking issues
(and NFS issues) by the way in which articles are stored to disk: the
article is written to a scratch directory, and then moved (via link() and
unlink() to prevent loss of data) to a storage location for new messages.
From there, the mail agent moves the message to a read-message area once
the message has been viewed. In all, a directory containing three
directories, and one file/inode per message, with the gain of complete
reliability.
A comparison of Maildir vs. mbox and MH folders is available in the qmail
distribution in "INSTALL.mbox":
ftp://koobera.math.uic.edu/pub/software/qmail-1.01.tar.gz
As well, QMail comes with a man page for maildir, which is available on
the web at:
http://www.qmail.org/qmail-manual-html/man5/maildir.html
It gives a concise description of precisely how maildir stores mail.
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