Hello,
We are having performance problems trying to migrate our pop/imap
servers to a new version. Our old servers are 4 debian lenny with 5GB of
RAM running of XenServer VMs with kernel 2.6.32-4-amd64 and dovecot
1.1.16. New servers are 4 ubuntu 12.04 with dovecot 2.1.5 running on
vmware vm with 6 cores and 16GB of RAM and kernel 3.2.0-24-generic. On
both server we are using nfs 3 with same configuration (regardless of
internal kernel differences, but we have no customized any of them, we
are using vanilla kernels with default configurations).
The problem we have is that new servers have performance problems. Even
when have a small part of our total users (about 25%) directed to the
new farm, performance is very poor, even useless.
Looking for NFS problems, we have found a lot of differences in nfs
operations. For example, this is the nfsstat of one of a new servers at
this moment:
myotis21:~# nfsstat
Client rpc stats:
calls retrans authrefrsh
414528349 885 37
Client nfs v3:
null getattr setattr lookup access
readlink
0 0% 95673837 23% 3961938 0% 89586364 21% 110097351 26%
2930961 0%
read write create mkdir symlink mknod
20009850 4% 6065319 1% 3757720 0% 1557 0% 0 0% 0
0%
remove rmdir rename link readdir
readdirplus
6378134 1% 281 0% 2602358 0% 555097 0% 53126619 12%
15615402 3%
fsstat fsinfo pathconf commit
113256 0% 26152 0% 0 0% 4026151 0%
and this is the same on one of the new ones:
amateo_adm@myotis31:~$ nfsstat
Server rpc stats:
calls badcalls badclnt badauth xdrcall
0 0 0 0 0
Client rpc stats:
calls retrans authrefrsh
178040318 675 178040800
Client nfs v3:
null getattr setattr lookup access
readlink
0 0% 24350345 13% 5045924 2% 10939469 6% 30185146 16% 142865
0%
read write create mkdir symlink mknod
8818016 4% 6058614 3% 2877653 1% 420 0% 0 0% 0
0%
remove rmdir rename link readdir
readdirplus
2842562 1% 69 0% 2961239 1% 634038 0% 0 0%
82921863 46%
fsstat fsinfo pathconf commit
70861 0% 18754 0% 9377 0% 152702 0%
Although nfs configuration is the same, there are a lot of differences
on readdir vs readdirplus nfs operations. In fact, in the old one we
have 12% readdir operations and 3% of readdirplus. And in the new one we
have 46% of readdirplus and no readdir operations.
Although readdirplus is supposed to be an optimization in nfs3, in
situations when you have big directories and uses just a few entries of
these directories it could be worse. So we think if this could be the
problem (or one of them).
Any idea of this difference? And if this difference could be
significative?
PS: I have attached doveconf -n of the new server.
--
Angel L. Mateo Martínez
Sección de Telemática
Área de Tecnologías de la Información
y las Comunicaciones Aplicadas (ATICA)
http://www.um.es/atica
Tfo: 868887590
Fax: 868888337
# 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_location = maildir:~/Maildir:INDEX=/var/indexes/%n
mail_nfs_storage = yes
mail_privileged_group = mail
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 = postmas...@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"
}
protocol pop3 {
pop3_logout_format = top=%t/%p, retr=%r/%b, del=%d/%m, size=%s, in=%i, out=%o
}
local 155.54.211.160/27/27 {
doveadm_password = ]dWhu5kB
}
