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From Jim Wright <j...@paneris.org>
Subject Re: IMAP Development Pointers
Date Wed, 03 Sep 2003 22:40:15 GMT
Hi Edward,

Edward Flick wrote:

>Just out of curiosity, is there anything wrong with just using the
>filesystem?  Folders work wonders :-P.  And sets of enumerated files for
>messages would be nice, easy, and quick to implement, and I guess some quick
>and easy link file for common boxes between accounts.  What do you think?
>Of course this is before really looking through much code.  But I like to
>get started on the right foot.
>  
>
I have University of Washington IMAP on my Linux machine
and use an experimental format mx which is as you describe.
To quote the docs:

. mx    This is an experimental format, and may be removed in a future
    release. ...
 
    [snip]

    mx is somewhat inefficient; the entire directory must be read
    and each file stat()'d.  We found it intolerable for a
    moderate sized mailbox (2000 messages) and have more or less
    abandoned it.   

    [snip]

 
    There's a general reason why file/message formats are a bad idea.
    Just about every filesystem in existance serializes file creation and
    deletions because these manipulate the free space map.  This turns out
    to be an enormous problem when you start creating/deleting more than a
    few messages per second; you spend all your time thrashing in the
    filesystem.

    It is also extremely slow to do a text search through a
    file/message format mailbox.  All of those open()s and close()s really
    add up to major filesystem thrashing.

I was not completely convinced by this. File system devices are getting
faster for a start.

Jim Wright

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