Performance issue

[Alessio Cecchi]

Hi,

try to start dovecot with "ulimits -u 10240 -n 40000" and increase the 
value in /proc/sys/fs/inotify/max_user_instances around to 1024.

I also suggest to use XFS instead of ext4, for example after a crash XFS 
is immediately available.

Ciao

Il 05/11/2014 16:07, absolutely_free at libero.it ha scritto:
> Hi,
> Since few days I noticed very high load on my mailserver (Centos 6.6 64bit, 8 GB RAM, 2 x  CPU 3.00GHz
> I am using Dovecot + Postfix + Roundcube + Nginx.
>
> I have about 10000 users.
> Spool is on network attached storage (Coraid).
>
> File system is ext4 (mounted with noatime).
>
> Problem appears almost every morning (while load is normal during afternoon).
>
> I suspect that this can be related to some user that have so many messages in his mailbox.
> How can I troubleshoot this?
>
> Here some messages that I got in maillog:
>
> Warning: Maildir: Scanning /var/spool/pop/domains/xxxx.it/YYYYYYYYY/Maildir/new took 71 seconds (1 readdir()s, 1 rename()s to cur/)
>
> Warning: Maildir /var/spool/pop/domains/zzzz/WWWWWWWWWWWW/Maildir/.Trash: Synchronization took 74 seconds (5 new msgs, 0 flag change attempts, 0 expunge attempts)
>
> dovecot: imap(xxxx at zzzz.it): Warning: Inotify instance limit for user 89 (UID postfix) exceeded, disabling. Increase /proc/sys/fs/inotify/max_user_instances
>
>
> tail: inotify cannot be used, reverting to polling: Too many open files
>
> My relevant dovecot conf:
>
> mail_location = maildir:/coraid-s2l2/domains
> namespace {
>    type = private
>    separator = .
>    prefix = INBOX.
>    inbox = yes
> }
> mail_uid = 89
> mail_gid = 89
> mail_fsync = never
> first_valid_uid = 89
> first_valid_gid = 89
> maildir_very_dirty_syncs = yes
> mbox_write_locks = fcntl
>
>
>
> thank you very much!