[Dovecot] Lot of dovecot process writes

[Angel L. Mateo]

Hello,

	While monitoring my servers' behaviour (ubuntu 12.04 with dovecot 
2.1.9, with about 70000 users) I have found that lots of disk usage is 
done by dovecot process (the parent process). Since lmtp, imap and pop3 
connections are handle by their own process, what could be the reason of 
this?

-- 
Angel L. Mateo Martínez
Sección de Telemática
Área de Tecnologías de la Información
y las Comunicaciones Aplicadas (ATICA)
http://www.um.es/atica
Tfo: 868889150
Fax: 868888337
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# 2.1.9: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.19um1 x86_64 Ubuntu 12.04.2 LTS 
auth_cache_size = 20 M
auth_cache_ttl = 1 days
auth_master_user_separator = *
auth_verbose = yes
default_process_limit = 1024
disable_plaintext_auth = no
log_timestamp = %Y-%m-%d %H:%M:%S
login_trusted_networks = 155.54.211.176/28
mail_access_groups = vmail
mail_gid = vmail
mail_location = maildir:~/Maildir:INDEX=/var/indexes/%2Ln/%Ln
mail_plugins = quota zlib lazy_expunge acl
mail_privileged_group = mail
maildir_very_dirty_syncs = yes
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
mdbox_rotate_size = 20 M
namespace {
  inbox = yes
  location = 
  prefix = 
  separator = .
}
namespace {
  hidden = yes
  list = no
  location = maildir:~/Maildir/expunged
  prefix = BORRADOS.
  separator = .
}
namespace {
  list = children
  location = maildir:%%h/Maildir:INDEX=~/Maildir/shared/%%u
  prefix = shared.%%u.
  separator = .
  subscriptions = no
  type = shared
}
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 cache_key=%Ln dovecot
  driver = pam
}
plugin {
  acl = vfile:/etc/dovecot/global-acls:cache_secs=3600
  lazy_expunge = BORRADOS.
  quota = dict:User quota::file:%h/Maildir/dovecot.quota
  quota_rule = *:storage=10G
  quota_rule2 = Trash:storage=+1G
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
  sieve_max_redirects = 15
  zlib_save = gz
  zlib_save_level = 6
}
postmaster_address = postmaster at um.es
protocols = imap pop3 lmtp sieve
service anvil {
  client_limit = 3075
}
service auth {
  client_limit = 4096
  unix_listener auth-userdb {
    mode = 0777
  }
}
service doveadm {
  inet_listener {
    port = 24245
  }
}
service imap {
  process_limit = 5120
  process_min_avail = 6
  vsz_limit = 512 M
}
service ipc {
  unix_listener ipc {
    user = dovecot
  }
}
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 = quota zlib lazy_expunge acl sieve
}
protocol imap {
  mail_plugins = quota zlib lazy_expunge acl imap_quota imap_acl
}
protocol lmtp {
  mail_plugins = quota zlib lazy_expunge acl sieve
}
protocol pop3 {
  pop3_logout_format = top=%t/%p, retr=%r/%b, del=%d/%m, in=%i, out=%o
}
local 155.54.211.160/27/27 {
  doveadm_password = <password>
}