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

[Scott Silva]

on 5/5/2011 1:04 AM Becker, Ronny spake the following:
> 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
> 
> 
What is the underlying filesystem, and if its ext3, is dir_index set on?