[Dovecot] New mailbox format

[Todd Vierling]

On Fri, 23 Sep 2005, dean gaudet wrote:

> here's one point where my thinking has differed -- i'd treat the mailbox
> files as read-only (plus one file which is append-only) and include an
> append-only modification log for recovery purposes...  read-only mailbox
> files permit compression,

Though they require sequential reading order for parsing, so think about
reading a bunch of messages from the end of the mbox:  one full
decompression for indexing, then very close to full decompression for every
message retrieval in the batch.  You'd think that retrieving a sequential
block via IMAP might help, but a lot of MUAs prefer single message random
access.

To address the situation you want, readonly archival, my vision would be a
compressed maildir (or equivalent), using each mail as a separately
compressed entry.  Zip is a pretty good format for this purpose.  Though
per-file compression is typically only about half as efficient as whole-mbox
compression, you'd have much faster search and retrieval if the file entries
had their own compression dictionaries.

-- 
-- Todd Vierling <tv at duh.org> <tv at pobox.com> <todd at vierling.name>