[Dovecot] blocked for xx secs

[Andrew Hearn]

Hello,

Occasionally (a few times a day) we get batches of Warnings in the log
such as:
 dovecot: Warning: chdir(/maildir/x.co.uk/users/y) blocked for 18 secs
This tends to last a minute or so for different users.

/maildir is a NFS mount, and I'm suspecting it's the NFS server being
busy and dovecot having to wait.

Other than replacing the NFS server with faster hardware is there
anything else we can do?

Indexes are local, and Maildir is on the NFS.

Dovecot 1.2.5
using:
mail_nfs_storage = yes
mmap_disable = no


NFS mounted as;
/maildir on /.automount/a.diskless/root/mail type nfs
(nosuid,nodev,noatime,vers=3,proto=tcp)


TIA
-- 
Andrew