On 3/16/2012 7:07 AM, Mauricio López Riffo wrote:
Hi,
We actually have a mail hosting solutions with aprox. 100 thousand
of email account, where about 90% of a customers use POP3 like email
configuration. About a few mounths (we perfomed a lot of migration
throught mbox email software to Maildir with dovecot) but i can see
that the performance is very poor and receive complaint about delays
of autentications of accounts.
The solution lives in Metrocluster Netapp storage, filesystem NFS,
VMware as a virtualization (the mtas are a virtual machines lives in
netapp too) about 4T of data mails and a 10G network connection
(betwen mtas and nfs storage) All account information work in LDAP
plataform (two servers in replicated mode, no high average or delays
detected in this servers)
When the traffic have a peak of 1800 concurrent connections POP3, all
of service suffer a high load average (about 8 - 20 load average in
each dovecot) and authenticacion takes about 2 -10 seconds (in low
traffic, autenticacion takes about 60 miliseconds)
Also, each dovecot instance lives un MTA server CentOS 5.8 x86_64 with
6G RAM (virtual machine) and share's hardware with a exim instance,
like a MTA relay system (autenticated relay)
Usage of network have peaks of 80Mbits (all dmz network have 1Gbits of
bandwith)
Attach of dovecot -n output:
# 2.0.18: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.18-308.1.1.el5 x86_64 CentOS release 5.8 (Final)
auth_debug_passwords = yes
auth_default_realm = portalplata.cl
auth_realms = portalplata.cl
auth_verbose = yes
auth_verbose_passwords = plain
auth_worker_max_count = 100
base_dir = /var/run/dovecot/
debug_log_path = /var/log/dovecot.log
default_process_limit = 200
default_vsz_limit = 512 M
disable_plaintext_auth = no
first_valid_gid = 12
first_valid_uid = 8
lock_method = dotlock
login_greeting = Dovecot mta10
mail_cache_min_mail_count = 5
mail_debug = yes
mail_fsync = always
mail_full_filesystem_access = yes
mail_gid = 12
mail_location =
maildir:%h/Maildir:INDEX=/data/cache/indexes/%2d/%1u/%2u/%u
mail_nfs_storage = yes
mail_plugins = " quota"
mail_uid = 8
maildir_copy_with_hardlinks = no
passdb {
args = /etc/dovecot/dovecot-ldap.conf.ext
driver = ldap
}
plugin {
mail_log_events = delete undelete expunge copy mailbox_delete
mailbox_rename
mail_log_fields = box from subject
quota = maildir
}
postmaster_address = m...@mail.com
protocols = imap pop3
sendmail_path = /usr/lib/sendmail
service auth {
unix_listener auth-userdb {
mode = 0600
user = exim
}
}
service imap-login {
service_count = 0
}
service imap-postlogin {
executable = script-login /usr/local/bin/postlogin.sh
user = root
}
service imap {
executable = imap imap-postlogin
}
service pop3-login {
inet_listener pop3s {
port = 995
ssl = yes
}
service_count = 0
}
service pop3 {
process_limit = 1024
}
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
ssl_key = </etc/pki/dovecot/private/dovecot.pem
userdb {
args = /etc/dovecot/dovecot-ldap.conf.ext
driver = ldap
}
verbose_proctitle = yes
protocol lmtp {
mail_plugins = " quota"
}
protocol lda {
mail_plugins = " quota"
}
protocol imap {
imap_capability =
mail_max_userip_connections = 10
mail_plugins = " quota autocreate notify quota imap_quota mail_log"
plugin {
autocreate = Sent Items
autocreate2 = Spam
autocreate3 = Drafts
autocreate4 = Trash
autosubscribe = Sent Items
autosubscribe2 = Spam
autosubscribe3 = Drafts
autosubscribe4 = Trash
}
}
protocol pop3 {
mail_plugins = " quota quota notify mail_log"
pop3_reuse_xuidl = yes
pop3_save_uidl = yes
pop3_uidl_format = %u
}
Output of account information in a LDAP:
# nettester, email.net, MAIL, USERS, cl
dn: uid=nettester,dc=email.net,o=MAIL,o=USERS,c=cl
dc: email.net
mailMessageStore: /export/mdir/3/12/nettes...@email.net/Maildir
uid: nettester
cn: nettes...@email.net
sn: nettes...@email.net
gidNumber: 12
homeDirectory: /export/mdir/3/12/nettes...@email.net
mail: nettes...@email.net
uidNumber: 8
objectClass: mailUser
objectClass: posixAccount
objectClass: mailSetting
loginShell: /bin/false
description: enable
service: pop3
service: imap
service2: webmail
mailRate: 200
mailQuota: 1024M
deliveryMode: none
mailReplyText: .
Any suggestions? All ideas will be have a good receptions ;)
Pd: Sorry my english
It doesn't seem to matter what type of hardware you might have, NFS can
cause real bottlenecks, even to the point that your machine may report
disk errors.
Unfortunately, it's an evil necessity in some shops, but any way to
eliminate NFS when large throughput is occurring will definitely help.
Make sure you're running the latest version of NFS on all machines since
V3 and V4 don't always like each other.
I don't have a solution for it's replacement other than expensive
hardware solutions.
steve
