[Dovecot] dovecot 2.1.5 performance

[Angel L. Mateo]

On 20/06/12 11:40, Angel L. Mateo wrote:
> Hello,
>
>      I'm migrating from 1.1.16 running in 4 debian lenny servers
> virtualized with xenserver and 1 core and 5GB of RAM to 2.1.5 running in
> 4 ubuntu 12.04 servers with 6 cpu cores and 16GB of RAM virtualized with
> VMWare, but I'm having lots a performance problems. I don't think that
> virtualization platform could be the problem, because the new servers
> running in xenserver has the same problems than running in vmware.
>
>      I have about 70000 user accounts, most of them without real
> activity (they are students who doesn't read his email or have its
> account redirected to other provider). I have about 700-1000 concurrent
> imap connections.
>
>      I have storage in nfs (nfsv3, the nfs server is a celerra), but
> indexes are in local filesystems (each server has its own index fs).
> Mailboxes are in maildir format.
>
>      Old servers and actual director servers are load balanced with an
> radware appdirector load balancer (the new backend servers don't need to
> be balanced because I'm using a director farm)
>
>      In the old platform I have scenario number 2 described at
> http://wiki2.dovecot.org/NFS, but in the new ones I have a director
> proxy directing all connections from each user to the same server (I
> don't specify any server for the user, director selects it according to
> the hash algorithm it has).
>
>      Some doubts I have for the recommended in that url:
>
> * mmap_disable: both single and multi server configurations have
> mmap_disable=yes but in index file section says that you need it if you
> have your index files stored in nfs. I have it stored locally. Do I need
> mmap_disable=yes? What it's the best?
> * dotlock_use_excl: it is set to no in both configurations, but the
> comment says that it is needed only in nfsv2. Since I have nfs3, I have
> it set it to yes.
> * mail_nfs_storage: In single server is set to no, but in multi server
> it set to yes. Since I have a director in front of my backend server,
> what is the recommended?
>
>      With this configuration, when I have a few connections (about
> 300-400 imap connections) everything is working fine, but when I
> disconnect the old servers and direct all my users' connections to the
> new servers I have lot of errors. server loads increments to over 300
> points, with a very high io wait. With atop, I could see that of my 6
> cores, I have one with almost 100% waiting for i/o and the other with
> almost 100% idle, but load of the server is very, very high.
>
>      With the old servers, I have performance problems, access to mail
> is slow, but it works. But with the new ones it doesn't work at all.
>
>      Any idea?
>
	I forgot attaching my doveconf.

-- 
Angel L. Mateo Martínez
Sección de Telemática
Área de Tecnologías de la Información       _o)
y las Comunicaciones Aplicadas (ATICA)      / \\
http://www.um.es/atica                    _(___V
Tfo: 868887590
Fax: 868888337


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# 2.1.5: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-24-generic x86_64 Ubuntu 12.04 LTS 
auth_cache_size = 20 M
auth_cache_ttl = 1 days
auth_debug = yes
auth_master_user_separator = *
auth_verbose = yes
default_process_limit = 1000
disable_plaintext_auth = no
log_timestamp = %Y-%m-%d %H:%M:%S
login_trusted_networks = 155.54.211.176/28
mail_debug = yes
mail_fsync = always
mail_location = maildir:~/Maildir:INDEX=/var/indexes/%n
mail_nfs_storage = yes
mail_privileged_group = mail
maildir_stat_dirs = yes
mdbox_rotate_size = 20 M
passdb {
  args = /etc/dovecot/master-users
  driver = passwd-file
  master = yes
  pass = yes
}
passdb {
  args = /etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
passdb {
  args = session=yes dovecot
  driver = pam
}
plugin {
  lazy_expunge = .EXPUNGED/ .DELETED/ .DELETED/.EXPUNGED/
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
  sieve_extensions = +imapflags
  sieve_max_redirects = 15
  zlib_save = gz
  zlib_save_level = 6
}
postmaster_address = postmaster at um.es
service anvil {
  client_limit = 2003
}
service auth {
  client_limit = 3000
  unix_listener auth-userdb {
    mode = 0666
  }
}
service doveadm {
  inet_listener {
    port = 24245
  }
}
service imap {
  process_limit = 5120
  process_min_avail = 6
  vsz_limit = 512 M
}
service lmtp {
  inet_listener lmtp {
    port = 24
  }
  process_min_avail = 10
  vsz_limit = 512 M
}
service pop3 {
  process_min_avail = 6
}
ssl = no
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
  driver = prefetch
}
userdb {
  args = /etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
protocol lda {
  mail_plugins = " sieve"
}
protocol lmtp {
  mail_plugins = " sieve"
}
local 155.54.211.160/27/27 {
  doveadm_password = ]dWhu5kB
}