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Date:      Mon, 27 Oct 2003 18:02:39 -0800
From:      Nathan Kay <mcnate@numenor.net>
To:        "Eric W. Bates" <ericx@vineyard.net>
Cc:        freebsd-isp@freebsd.org
Subject:   Re: consequences of migrating to maildir storage system
Message-ID:  <20031028020239.GA74323@numenor.net>
In-Reply-To: <0ac901c393ea$4bc1ac80$68c311cc@fortiva>
References:  <0ac901c393ea$4bc1ac80$68c311cc@fortiva>

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On Thu, Oct 16, 2003 at 09:34:56AM -0400, Eric W. Bates wrote:
> Anyone have unfortunate experiences as a consequence of converting
> mail storage from flat file (mbox) to maildir? I'm concerned that the
> increase in the number of files might cause problems with replication
> (we use rsync), backup or even just running out of inodes.

	The two issues that I've seen with maildir and large mail
environments are both file system related. First, watch your inodes, you
may find yourself eating them up quickly. As noted already in the
thread, newfs options can solve this issue.

	The other thing to watch out for, depending on your userbase and
usage patterns is lost space from files smaller that your block size.

	That is to say, if your file system block size is 16k, and most
of the email messages are 1k, that's 15k per message (on average) that
you've lost, unless the file system is doing things to avoid it.

	Also, if you're using a network file system that pre-fetches
file and directory attributes, you may eventually want to look into what
your cache miss rates are for that.

	Depending on the usage patterns, pre-fetching file and directory
attributes for network mounted file systems that are storing maildirs
can be either a very good thing, or a very bad thing. Depends on your
cache miss rates.

-- 
Nathan Kay
Numenorean Networks
http://www.numenor.net
PGP Public Key: http://www.numenor.net/~mentat/pgp.asc

"Unix is like a Vorlon: It's incredibly powerful, gives terse,
 cryptic answers, and has a lot of things going on in the
 background."



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