[Dovecot] the most serius problems [part 1]

Farkas Levente lfarkas at bnap.hu
Thu May 29 23:22:17 EEST 2003

Mark E. Mallett wrote:
> On Wed, May 28, 2003 at 01:46:33PM +0200, Farkas Levente wrote:
>>the first on is the load.
>>has anybody else use dovecot in a real enviromnt with at least hundreds 
>>of users and at least 50 concurrent user at the same time?
>>it seems to me no one else just me.
> That seems like an awfully high percentage of users connecting- if I
> assume "hundreds" might mean 300, 1 out of every 6 users is connected
> at any given time?
> One of the servers running dovecot here has thousands of users.  During
> the middle of the day I typically see 17-20 users connected at any
> given time.  This has been known to increase to 50+ especially during
> prime time (evening).  Over a period of 24 hours dovecot logins occur
> at the rate of around 2.5 logins per second.  Now- most of our users
> are using POP rather than IMAP, but there is still a reasonable amount
> of IMAP activity.  Plus I'm not sure that detail matters: POP logins
> use resources too, perhaps repeated POP logins use more than
> constantly-connected imap sessions.
> The load on the server due to dovecot is negligable.  Most of the load
> is due to handling incoming mail.  Obviously you are seeing something
> different- perhaps you are using features that we are not.
> I rather wish dovecot would log some more statistics, as I think has
> been mentioned already- like a record for logout as well as one for
> login, including number of messages scanned, left on server,
> downloaded, and deleted, plus total bytes transferred).  These numbers
> would give a better picture of what's going on.

the reason is simple there are about 300 users when they come in at the 
morning thay simple start OE6 and never exit from it just when they go 
home (why do they do so?). so in the prime I saw 126 imap connection at 
the same time. and most user has a real big mailboxes without any 
organization/folders (just inbox, sent and drafts). incoming mails are 
handled by postfix which is realy fast, reliable and almost no load at 
all. here everybody use imap since most people doesn't have an own desk 
(only 50 has) so everybody just sit down to the first free desk. in this 
case only the imap is the solution.
the real load comes when indexing or reindexing is running (eg. if we 
delete all index file for same reason). in this case even 10 imap 
connections are able to create a load about 10 (while the cpu are 95% 
idle). and there is something wrong with 0.99.9 series. since now when 
I've to switch back to 0.99.8 it's a lot faster.

   Levente                               "Si vis pacem para bellum!"

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