[Mailman-Developers] What happens with mailman after a crash

[Barry Warsaw]

On Tue, 2004-01-27 at 13:40, John Dennis wrote:

> Doesn't the new SYNC_AFTER_WRITE flag address this issue? Here is the doc
> for it:
> 
> # This flag causes Mailman to fsync() its data files after writing and
> # flushing its contents.  While this ensures the data is written to disk,
> # avoiding data loss, it may be a performance killer.  Note that this flag
> # affects both message pickles and MailList config.pck files.

Note that this warning /may/ be superstition.  When I did some tests a
long while ago, I saw something like a 95% hit in performance on
ext3/RH9.  Since then, I've been told that others have seen much less of
a performance hit, and I've also heard that RH9 is particularly prone to
performance problems when under heavy I/O.

It would be nice for folks out there to enable SYNC_AFTER_WRITE on heavy
traffic sites and report back on performance.  Maybe we should enable
this option by default.

Also, I now know how to cut the number of files created and unlinked by
Mailman in half.  Currently, the qrunners create a .msg and .db file for
every message in the queues.  I can collapse that to one file, and I
think I can do this while still maintaining the Python 2.1 compatibility
requirement.  I think the upgrade procedure will be fairly
straightforward, so I'm seriously considering implementing this for
Mailman 2.1.5.  It's an important change, but it's mostly internal and I
think it would be a big enough win to slip it into a bug fix release. 
There are other advantages, such as getting rid of those pesky "lost
data files for filebase" messages.

-Barry