[Dovecot] Dovecot extremely slow!

[Robin]

On 9/26/2013 7:47 AM, Patricio Rojo wrote:

> * /home partition nfs mounted from a remote firewalled QNAP NAS server
> (TS-869U-RP), which also serves other machines (RAID-5 setup with
> currently no bad disks).

I assume this NAS properly implements various locking services? 
Dovecot, like most mail MUA + MTAs, makes use of various filesystem 
locking primitives to maintain conherence in a multi-user access 
scenario.  If QNAP's stack doesn't implement proper NFS locking, this is 
probably a cause of these odd lags.

You can probably add a "nolock" to your /etc/fstab to resolve it, but 
you risk mailbox corruption.

You mentioned it was firewalled... are you allowing the lockd port 
through to the QNAP from the Dovecot machine that's mounting it?  NFS2 + 
3 implement locking via communication with a "lock manager" that listens 
on port 4045, if I recall.

=R=