[Dovecot] Dovecot performance issues with many writes

[Andy Robbins]

# dovecot -n
# 1.2.9: //etc/dovecot.conf
# OS: Linux 2.6.18-164.9.1.el5 x86_64 CentOS release 5.4 (Final)
base_dir: /var/run/dovecot/
log_path: /var/log/dovecot.log
protocols: imap pop3
ssl_cert_file: /etc/postfix/ssl/smtp1.domain.com.cert
ssl_key_file: /etc/postfix/ssl/smtp1.domain.com.key
disable_plaintext_auth: no
login_dir: /var/run/dovecot//login
login_executable(default): //libexec/dovecot/imap-login
login_executable(imap): //libexec/dovecot/imap-login
login_executable(pop3): //libexec/dovecot/pop3-login
login_user: postfix
login_greeting: Welcome
login_process_per_connection: no
login_processes_count: 2
mail_max_userip_connections: 50
mail_uid: 500
mail_gid: 500
mail_location: maildir:~/Maildir
mail_debug: yes
mmap_disable: yes
mail_nfs_storage: yes
mail_nfs_index: yes
mail_executable(default): /etc/dovecot/last-login-imap.sh
mail_executable(imap): /etc/dovecot/last-login-imap.sh
mail_executable(pop3): /etc/dovecot/last-login-pop3.sh
mail_plugins: quota
mail_plugin_dir(default): //lib/dovecot/imap
mail_plugin_dir(imap): //lib/dovecot/imap
mail_plugin_dir(pop3): //lib/dovecot/pop3
pop3_uidl_format: %f
lda:
  postmaster_address: postmaster at domain.com
  auth_socket_path: /var/run/dovecot/auth-master
  log_path: /var/log/dovecot-deliver.log
  info_log_path: /var/log/dovecot-deliver.log
  fsync_disable: no
auth default:
  mechanisms: PLAIN LOGIN CRAM-MD5 DIGEST-MD5 APOP
  user: vmail
  username_translation: %@
  verbose: yes
  passdb:
    driver: ldap
    args: /etc/dovecot/dovecot-ldap.conf
  userdb:
    driver: ldap
    args: /etc/dovecot/dovecot-ldap.conf
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: postfix
    master:
      path: /var/run/dovecot/auth-master
      mode: 384
      user: vmail
      group: vmail
plugin:
  quota: maildir:User quota
  quota_rule: *:storage=0