[lug] imap performance

[Bear Giles]

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Hugh Brown wrote:
| Alternatively, is there an optimal size for mailbox files?  Is
there a
| size that doesn't cause massive slow downs, but doesn't require
having
| lots of little mailbox files.

"Lots of little files" is only an issue if you have a file system
that does a sequential scan of the directory, or a large block size.

The latter is easy to fix, and should be standard on any mail or
news spool partition.  You'll probably have to reformat the
partition to specify a smaller block size, but you can usually
recover a *lot* of unused disk space if you drop to a 1k block
instead of a standard 4k block.  The latter is reasonable on a
mixed-use partition where you have lots of images, libraries,
etc., but text messages are heavily skewed towards smaller files.

The former is slightly more complex... but I think all of the
journaling filesystems use a B-tree (or something similar) for
their directories.  It doesn't make a lot of difference for a few
hundred entries, but if you're sequentially scanning a directory
with thousands of entries it can have a huge impact.

I'm currently testing Courier (maildir) on JFS, but can't yet say
much beyond "it works."

Bear
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