Hello,  i have some question about NFS, dovecot director, and imap settings.

I was reading all dovecot documentation ad mail lists, but some aspect  are not clear to me.

I am looking for performance / tunning my infra to work in a more efficient way because we experiences some issues some days ago.

This is my infra:

I got an infra with 2 dovecot-directors and 3 imap backend.
I got all the emails stored in a common NFS share filer to all the imap nodes. ( Index are locally stored in each imap node.)


My NFS mount options:

(0)#: nfsstat -m

/data/mail from myipaddress:/export/mail/maildirs
 Flags: rw,nosuid,noexec,noatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,nordirplus,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.0.0.205,mountvers=3,mountport=20048,mountproto=tcp,local_lock=none,addr=10.0.0.205

Questions:  ( https://wiki.dovecot.org/PerformanceTuning , https://doc.dovecot.org/configuration_manual/nfs/  >> i am following these steps )

1) Is my NFS correct setup with the mount options well optimized ?  Not sure if someone is using the same flags that me or got a better recomendation to used.

2) Set mmap_disable = yes ???   >>  This must be set to yes if you store indexes to shared filesystems. In my case i got them locally in each imap node not in NFS share folder.

>> High performance NFS setup with indexes on local disk (see below for benefits):

mmap_disable = no

3) Set mail_fsync = always  ???

Documentation: https://wiki.dovecot.org/PerformanceTuning

always

    Use fsync after all disk writes.

    Recommended for NFS to make sure there aren’t any delayed write()s.

3.a) where i can setup this option mail_fsync = always , because i run  doveconf -n in director,  and imap nodes, and they are not showing nothing.

3.b) In which node ? Do i need to add  the setting in dovecot.conf in director node or in imap node or in both ?  Not sure if this is the correct way:

0)#: doveconf -n
# 2.3.13 (89f716dc2): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.13 (cdd19fe3)
# OS: Linux 5.10.0-20-amd64 x86_64 Debian 11.6

mail_debug = yes
mail_fsync = always
mail_max_userip_connections = 20
mail_nfs_storage = yes
mail_plugins = " notify mail_log"
mail_privileged_group = mail



protocol lmtp {
  mail_fsync = always
  mail_plugins = " notify mail_log sieve mail_lua push_notification push_notification_lua"
  plugin {
   ...
  }

4) Do not set mail_nfs_index or mail_nfs_storage (i.e. keep them as no)   ?????

First option make sense but the second one not.

https://doc.dovecot.org/settings/core/#core_setting-mail_nfs_storage

mail_nfs_storage

        Default: no

        Values: Boolean

    Flush NFS caches whenever it is necessary to do so.

    This setting should only be enabled if you are using multiple servers on NFS.

So should be possible to enable this option   mail_nfs_storage = yes ?????




4) I got this setting in dovecot-sql.conf  ( director ) 

driver = mysql
connect = host=myserver.X dbname=maildb user=dovecot password=XXXXXXXXXXXXXXXX
default_pass_scheme = SHA
password_query = select login as user, crypt_sha1 as password, home as userdb_home, uid AS userdb_uid, gid AS userdb_gid, concat(maildir,':INDEX=/data/indexes/',login) as userdb_mail from mailbox left join aliases on aliases.systemid = aliasid where login = '%u' and inactive = 0;
user_query = select home, maildir as mail, uid, gid from mailbox left join aliases on aliases.systemid = aliasid where login = '%u' and inactive = 0;
iterate_query = select distinct login as user from mailbox;

I would like to implement  ITERINDEX  and probably VOLATILEDIR but not sure if this is the correct change or if i need to change something into the database.

from:

password_query = select login as user, crypt_sha1 as password, home as userdb_home, uid AS userdb_uid, gid AS userdb_gid, concat(maildir,':INDEX=/data/indexes/',login) as userdb_mail from mailbox left join aliases on aliases.systemid = aliasid where login = '%u' and inactive = 0;

to: