On 22 Jul 2014, at 04:57, Murray Trainer <mtrai...@westnet.com.au> wrote:
> 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) Does relatime work with NFS? If yes, changing it to noatime would save some I/O. maildir_very_dirty_syncs=yes should be helpful. > # 2.2.9: /etc/dovecot/dovecot.conf mailbox_list_index=yes might be useful, although it has had some further performance improvements since v2.2.13. I should try to make v2.2.14 soon.. > quota = maildir Dict file quota would be a bit faster than maildir++ quota.