dovecot - Jan 2013 - Benchmarking: Dovecot vs Courier. Courier wins as POP3 server

Hi All,

I have compared Dovecot performance to Courier and it appears that as a POP3
server Dovecot is slower in 2 times but as an IMAP server it is faster in 1.5
times. The same node (16CPUs), testing time is 30 min, please see results and
dovecot configs attached.
Benchmark software is MStone used by Sendmail Inc so is is quite reliable.

I do not see anything else to tweak in Dovecot to increase POP3 performance. Can
we all have some tips to improve it please ?

This is how my Dovecot set up:
(LDAP user) -> Dovecot Director -> (Master user) -> Dovecot

Dovecot Director:
dovecot-shared-4:~# /usr/local/dovecot/bin/doveconf -n -c
/usr/local/dovecot/etc/dovecot/dovecot-proxy.conf
# 2.1.12: /usr/local/dovecot/etc/dovecot/dovecot-proxy.conf
# OS: Linux 2.6.32-5-amd64 x86_64 Debian 6.0.6
auth_debug = yes
auth_mechanisms = plain login cram-md5 ntlm
auth_verbose = yes
base_dir = /var/run/dovecot-proxy
default_internal_user = webmail
director_mail_servers = 192.168.100.102
director_servers = 192.168.100.101
disable_plaintext_auth = no
doveadm_password = blah
doveadm_proxy_port = 9292
instance_name = dovecot-proxy
listen = 192.168.100.101
log_path = /var/log/dovecot-proxy.log
login_greeting = Dovecot Proxy ready.
mail_location = maildir:~/
passdb {
  args = /usr/local/dovecot/etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
service auth-worker {
  user = webmail
}
service auth {
  client_limit = 2400
}
service director {
  fifo_listener login/proxy-notify {
    mode = 0666
  }
  inet_listener {
    port = 9191
  }
  unix_listener director-userdb {
    mode = 0600
  }
  unix_listener login/director {
    mode = 0666
  }
}
service doveadm {
  inet_listener {
    port = 9292
  }
}
service imap-login {
  executable = imap-login director
  inet_listener imap {
    port = 143
  }
  inet_listener imaps {
    port = 993
    ssl = yes
  }
}
service imap {
  service_count = 0
}
service lmtp {
  inet_listener lmtp {
    port = 24
  }
}
service pop3-login {
  executable = pop3-login director
  inet_listener pop3 {
    port = 110
  }
  inet_listener pop3s {
    port = 995
    ssl = yes
  }
}
service pop3 {
  service_count = 0
}
ssl_cert = </usr/local/dovecot/ssl/dovecot.pem
ssl_key = </usr/local/dovecot/ssl/dovecot.pem
userdb {
  args = /usr/local/dovecot/etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
protocol imap {
  mail_max_userip_connections = 100
}
protocol doveadm {
  auth_socket_path = director-userdb
}

Dovecot (back-end):
dovecot-shared-4:~# /usr/local/dovecot/bin/doveconf -n
# 2.1.12: /usr/local/dovecot/etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-5-amd64 x86_64 Debian 6.0.6
auth_debug = yes
auth_master_user_separator = *
auth_mechanisms = plain login
auth_verbose = yes
base_dir = /var/run/dovecot/
default_internal_user = webmail
disable_plaintext_auth = no
doveadm_password = blah
listen = 192.168.100.102
log_path = /var/log/dovecot.log
mail_fsync = always
mail_location = maildir:~/
mail_nfs_index = yes
mail_nfs_storage = yes
mail_plugins = " quota fts fts_lucene"
mmap_disable = yes
namespace {
  inbox = yes
  location   prefix = INBOX.
  separator = .
}
passdb {
  args = /usr/local/dovecot/etc/dovecot/passwd.masterusers
  driver = passwd-file
  master = yes
  pass = yes
}
passdb {
  driver = static
}
plugin {
  fts = lucene
  fts_lucene = whitespace_chars=@.
  quota = maildir:User quota
}
service director {
  unix_listener director-admin {
    mode = 00
  }
}
service doveadm {
  inet_listener {
    port = 9292
  }
}
service imap-login {
  inet_listener imap {
    port = 143
  }
  inet_listener imaps {
    port = 993
    ssl = yes
  }
  process_limit = 20
  process_min_avail = 8
}
service imap-postlogin {
  executable = script-login /usr/local/dovecot/bin/imap-postlogin.sh
  user = webmail
}
service imap {
  executable = imap imap-postlogin
}
service lmtp {
  inet_listener lmtp {
    port = 24
  }
}
service pop3-login {
  inet_listener pop3 {
    port = 110
  }
  inet_listener pop3s {
    port = 995
    ssl = yes
  }
  process_limit = 20
  process_min_avail = 8
}
service pop3-postlogin {
  executable = script-login /usr/local/dovecot/bin/pop3-postlogin.sh
  user = webmail
}
service pop3 {
  executable = pop3 pop3-postlogin
}
ssl_cert = </usr/local/dovecot/ssl/dovecot.pem
ssl_key = </usr/local/dovecot/ssl/dovecot.pem
userdb {
  args = /usr/local/dovecot/etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
protocol imap {
  mail_plugins = " quota fts fts_lucene imap_quota"
}

Best Regards,
Alexandr Sabitov
Netregistry
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On 17.1.2013, at 1.47, Alexandr Sabitov <alexandr.sabitov at
netregistry.com.au> wrote:
> I do not see anything else to tweak in Dovecot to increase POP3
performance. Can we all have some tips to improve it please ?
> 
> mail_fsync = always
Courier POP3 does no fsyncing. Although I'm not sure how much difference it
makes with NFS.
> mail_nfs_index = yes
> mail_nfs_storage = yes
Both of these are unnecessary and slow things down.

Also you should add:

pop3_no_flag_updates = yes

On 17.1.2013, at 6.23, Timo Sirainen <tss at iki.fi> wrote:
> On 17.1.2013, at 1.47, Alexandr Sabitov <alexandr.sabitov at
netregistry.com.au> wrote:
> 
>> I do not see anything else to tweak in Dovecot to increase POP3
performance. Can we all have some tips to improve it please ?
Oh, and because of Dovecot index files it has to do a bit more work than
Courier, so with indexes Dovecot POP3 is probably slower for POP3 clients that
download+delete all mails, but faster when POP3 clients leave (a lot of) mail
lying around on the server. You could get Courier-like unindexed behavior by
setting:

mail_location = maildir:~/:INDEX=MEMORY

On Wed, 16 Jan 2013 23:47:33 +0000 Alexandr Sabitov
wrote:
> Hi All,
> 
> I have compared Dovecot performance to Courier and it appears that as a
POP3 server Dovecot is slower in 2 times but as an IMAP server it is faster in
1.5 times. The same node (16CPUs), testing time is 30 min, please see results
and dovecot configs attached.
> Benchmark software is MStone used by Sendmail Inc so is is quite reliable.
> 
> I do not see anything else to tweak in Dovecot to increase POP3
performance. Can we all have some tips to improve it please ?
The Middle Age has called, it wants POP3 back.

--Frank Elsner

Am 17.01.2013 08:30, schrieb Frank Elsner:
> On Wed, 16 Jan 2013 23:47:33 +0000 Alexandr Sabitov wrote:
>> Hi All,
>>
>> I have compared Dovecot performance to Courier and it appears that as a
POP3 server Dovecot is slower in 2 times but as an IMAP server it is faster in
1.5 times. The same node (16CPUs), testing time is 30 min, please see results
and dovecot configs attached.
>> Benchmark software is MStone used by Sendmail Inc so is is quite
reliable.
>>
>> I do not see anything else to tweak in Dovecot to increase POP3
performance. Can we all have some tips to improve it please ?
> 
> The Middle Age has called, it wants POP3 back.
> 
> --Frank Elsner
> 
i have about 1000 pop3 tls logins per minute with dovecot ( one server )
( real users ! ) so its simply fast enough,
in real live , after optimize dovecot setup to your needs,
at some point you will use loadbalancers/directors etc
to pump up performance  thats for all pop3 server you might use


Best Regards
MfG Robert Schetterer

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