HI All,

We have a couple of dovecot director proxies and six backed mailstores each accessing mailboxes stored on five NFSv4 filsystems with about 1TB of mail on each in maildir format.  We have about 800 max users on each mailstore at peak times and performance appears to starting to degrade at these times.  The mailstores are pretty recent hardware with 64GB of RAM and 24 cores.   The NFS storage is EMC VNX and we are doing about 250 I/O per sec upto max of 500 on each filesystem.   I need to squeeze more performance out of these servers whether that is in the NFS client, Dovecot or Linux OS/kernel areas.   We use LDAP for auth and I am doing some tuning in that area.   The NFS filesystems are mounted with the options below:

10.11.0.238:/mailbox_store_01 on /home1 type nfs4 (rw,relatime,vers=4.0,rsize=65536,wsize=65536,namlen=255,hard,nordirplus,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=10.11.0.96,local_lock=none,addr=10.11.0.238)

My dovecot config is below.  I am not seeing any obvious issues in the server logs.    Any suggestions on how to improve performance would be appreciated.

Thanks

Murray

# doveconf -n # 2.2.9: /etc/dovecot/dovecot.conf doveconf: Warning: service auth { client_limit=40960 } is lower than required under max. load (41280) doveconf: Warning: service anvil { client_limit=40970 } is lower than required under max. load (41183) # OS: Linux 3.13-0.bpo.1-amd64 x86_64 Debian 7.5 auth_cache_size = 64 M auth_cache_ttl = 2 hours auth_failure_delay = 0 auth_mechanisms = plain login auth_username_chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!#$-=?^_{}~./@+%" auth_username_translation = +@ auth_worker_max_count = 256 base_dir = /var/run/dovecot/ disable_plaintext_auth = no first_valid_gid = 1001 first_valid_uid = 1001 mail_fsync = always mail_location = maildir:~/ 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 mmap_disable = yes namespace { inbox = yes location = prefix = INBOX. type = private } passdb { args = /etc/dovecot/dovecot-ldap.conf.ext driver = ldap } plugin { acl = vfile quota = maildir quota_rule = INBOX.Trash:ignore } protocols = " imap lmtp sieve pop3" service anvil { client_limit = 40970 } service auth-worker { user = dovecot } service auth { client_limit = 40960 unix_listener auth-userdb { group = mail mode = 0666 user = dovecot } } service imap-login { chroot = login inet_listener imap { address = *, [::] port = 143 } inet_listener imaps { address = * port = 993 ssl = yes } process_limit = 20480 process_min_avail = 32 service_count = 1 user = dovecot vsz_limit = 256 M } service imap { process_limit = 40960 vsz_limit = 256 M } service lmtp { inet_listener lmtp { address = 27.54.95.41 port = 24 } process_min_avail = 32 } service managesieve-login { client_limit = 40960 process_limit = 120 process_min_avail = 5 service_count = 0 vsz_limit = 64 M } service managesieve { process_limit = 4096 vsz_limit = 256 M } service pop3-login { chroot = login inet_listener pop3 { address = *, [::] port = 110 } inet_listener pop3s { address = * port = 995 ssl = yes } process_limit = 20480 process_min_avail = 32 service_count = 1 user = dovecot vsz_limit = 256 M } service pop3 { process_limit = 40960 vsz_limit = 256 M } ssl_cert =