[Dovecot] Dovecot very slow on a mailbox with > 700 IMAP Folders

[Becker, Ronny]

Hello,
I am using Dovecot 1.2.9 on a 32bit on Ubuntu 10.04.2 LTS.

We got one user who uses folders in an "exessive" way. He has got 704 
subscribed folders. That means about nearly 3000 folders on the 
filesystem. Since ~ a week the user couldn't work because of timeouts 
when connecting to Dovecot (IMAP). Thunderbird doesn't show any folders 
- timeout - the webmail System (Groupoffice) only presents the INBOX.

I did some debugging and found that a lsub "" "*" that is used by 
Thunderbird takes > 5 minutes. Thunderbird disconnects after ~1 Minute 
showing the timeout. I entered the command directly via port 
communication. So this is no clientside problem. But there is no error 
message or something else in any logs.

I did some debugging with strace, too. It's about 22MB only for running 
the lsub command !? The Mailbox size is about ~2.2GB, so this should be 
no problem. The maximum subfolder level is about 13 - could this be a 
problem? You can find the structure (simply shown) attached.


Thanks for any help!!


Best regards
Ronny Becker


-- 
Mit freundlichen Grüßen,
Ronny Becker

Institut für Medizinische Diagnostik GmbH
Ingelheim / Datenverarbeitung
Konrad Adenauer Strasse 17
55218 Ingelheim
Telefon: 06132 781 249
Fax: 06132 781 9 249

ronny.becker at bioscientia.de
www.bioscientia.de

Gesellschaft mit beschränkter Haftung mit Sitz in 55218 Ingelheim am Rhein, eingetragen im Handelsregister des Amtsgerichts Mainz unter HRB 21166.
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