On Sunday 25 March 2007 21:24, Kyle Wheeler wrote:
> On Sunday, March 25 at 09:48 PM, quoth John Levine:
> > It might be useful if you have a pool of servers sharing a single
> > database of pop-before-smtp,
>
> Hmm, fair enough. Still seems like overkill, though.
>
> > but I would think for that application NFS would be adequate.
>
> Agreed.
>
Actually, it isn't. I worked on a cluster of about 10 front-end
qmail/vpopmail servers serving ~6000 users and handling ~200K messages/day.
At the height of the busy times, with literally 100+ pop/imap
connections/second, the tcp.smtp cdb couldn't get rebuilt fast enough to
avoid collisions. Since vpopmail keeps a dynamic list of IP addresses in (in
our case) a MySQL DB, and has to combine it with the static list from the FS,
it was rebuilding the tcp.smtp.cdb file 100 times/second, which is NOT where
CDB excels. The solution for us was to use the tcpserver MySQL patch which
checks checks the MySQL table in a read-only manner, and let vpopmail handle
the updates. Which, incidentally, is what the original patch author wrote it
for...
This new patch does seem like it could be overkill, but I haven't really
looked at it closely - I just wanted to chime in on the viability (or lack
thereof) of an NFS mount handling high-volume CDB rebuilds.
Josh
--
Joshua Megerman
SJGames MIB #5273 - OGRE AI Testing Division
You can't win; You can't break even; You can't even quit the game.
- Layman's translation of the Laws of Thermodynamics
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