Re: concerning dovecot settings for high volume server

13 Sep 2015


      ----- Original Message -----
From: Tony Morehen [mailto:tmorehen@ajmconsulting.ca]
To: dovecot@dovecot.org
Sent: Sat, 12 Sep 2015 17:57:27 -0400
Subject: Re: concerning dovecot settings for high volume server
You may be running up against Linux system/user limits.  Run
$ cat /proc/sys/kernel/pid_max
and
$ ulimit -a
That should give some insight into your problem.
On 12/09/2015 2:53 PM, Rajesh M wrote:
...
hi
centos 6 64 bit
hex core processor with hyperthreading ie display shows 12 cores
16 gb ram
600 gb 15000 rpm drive
we are having around 4000 users on a server
i wish to allow 1500 pop3 and 1500 imap connections simultaneously.
need help regarding the settings to handle the above
imap-login, pop3-login
imap pop3 service settings
i recently i got an error
imap-login: Error: read(imap) failed: Remote closed connection (process_limit reached?)
my current dovecot config file
# 2.2.7: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-431.23.3.el6.x86_64 x86_64 CentOS release 6.5 (Final)
auth_cache_negative_ttl = 0
auth_cache_ttl = 0
auth_mechanisms = plain login digest-md5 cram-md5
default_login_user = vpopmail
disable_plaintext_auth = no
first_valid_gid = 89
first_valid_uid = 89
log_path = /var/log/dovecot.log
login_greeting = ready.
mail_max_userip_connections = 50
mail_plugins = " quota"
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave
namespace {
inbox = yes
location =
prefix =
separator = .
type = private
}
passdb {
args = cache_key=%u webmail=127.0.0.1
driver = vpopmail
}
plugin {
quota = maildir:ignore=Trash
quota_rule = ?:storage=0
}
protocols = imap pop3
service imap-login {
client_limit = 256
process_limit = 400
process_min_avail = 4
service_count = 0
vsz_limit = 512 M
}
service pop3-login {
client_limit = 1000
process_limit = 400
process_min_avail = 12
service_count = 0
vsz_limit = 512 M
}
ssl_cert = 
thanks very much,
rajesh
this is the first time i got this message since past over an year.
the error went away as soon as i restarted dovecot..
surprisingly this happened in the night ie off-office hours.
here are the values i got
also could you provide me the settings for the limits if wish to handle around 1500 simultaneous connections of pop3 and imap each ?
the current values are as follows
[root@ns1 log]# cat /proc/sys/kernel/pid_max
49152
[root@ns1 log]# ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 127047
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 127047
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
thanks
rajesh