NFSv4 delegation

[brd]

hi all,
i'm managing a large installation of a dovecot cluster in director + NFS
backend architecture and we are moving from NFSv3 to NFSv4. Our NFS
server is a Netapp in clustered mode and reading technical specs of
NFSv4 delegation feature it seems that enabling delegation in this type of
dovecot architecture should bring great benefits: only one backend server access
a specific mailbox at a time (even deliveries are managed by director hashing
via LMTP) so the getattr rpc calls should decrease significantly while the risk of
conflicting delegations is very low (impacting negatively on the benefits obtainable).
Can anyone confirm this hypothesis?

I've heard that the linux implementation of NFSv4 delegation is mature
only for read delegation (and not yet for write delegation): is this
true? And, if true, could this fact limit the benefits of activating NFS
delegation feature?


Best regards

-brd