Hello Markus,
Am 2008-07-10 18:09:09, schrieb Markus Krause:
The Problem:
Sometimes we were getting a load of up to 250 (!), thats when we kill some
Wow, nice load. Does kill work on such load?
all of the imapd deamons or have to reboot the machine. We are using
uw-imap, no ssl/tls (at the moment). The load immediatly goes down if we
So you are using Mailbox format for imap?
This is WHY you get this load...
My Zenit Data Systems Express5800 (4x Xeon 550MHz with 4 GByte of memory)
has 1300 Users and does not run into this load and locking problem...
I am using "courier-imap" and I sugest you to migrate to Maildir which
mean, you can put for each /usr/spool/mail/${USER}/ directory a symlink
and you wil never run into problems with procmail.
kill enough imapd. During the high load the cpu usage is about 60 % idle,
the network traffic is normal but the disk i/o is near 100% all the time.
This is normaly with mailbox format. Switch to Maildir!
Thats why we thought of distributing the users folders on (for the first)
three independant RAID5 disk arrays to see if this really is the bottleneck.
I do not use Raid-5...
Each of the 5 sets is Raid-1 with three 300 GByte SCSI drives and 300
Users which mean 1 GByte per $USER. (the third drive is the HotFix)
Unfortunately this problem does not occure all the time :
- it has been seen mostly just before 6 pm, so it seems as everyone is
reading his email just before going home ... But not every day ...
- we have seen this while 60 users where using imap, and we have seen a load
of 4 if 300 users are connected
:-) Again: Use Maildir!
- maybe one problem is the size of our users mailboxes, some (about 25) have
inboxes of over 1.5 GB (and refuse to change this, no way to solve this
here) and about additional 60 have more than 1 GB ... Don't know if this
causes a problem with imapd (uw-imap) but this is a point we can not change
I do not know, why, but I am 99% sure, your uw-imap is using mailbox. ;-)
2) is there a way to prevent procmail from checking if the default mailbox
is "bogus"?
best and uncomplicated one would be creating a unix account per $USER and
set "SHELL=/bin/false" and then use Maildir
3) how are you handling such problems?
I have stoped using virtul users and created Unix-Accounts from a script.
It saved me very much time trouble shooting...
Thanks, Greetings and nice Day/Evening
Michelle Konzack
Systemadministrator
24V Electronic Engineer
Tamay Dogan Network
Debian GNU/Linux Consultant
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