Zimbra will support customers that store backups (e.g. /opt/zimbra/backup) on an NFS-mounted partition. Note that this does not relieve the customer from the responsibility of providing a storage system with a performance level appropriate to their desired backup and restore times. In our experience, network-based storage access is more likely to encounter latency or disconnects than is equivalent storage attached by fiber channel or direct SCSI.
Zimbra continues to view NFS storage of other parts of the system as unsupported. Our testing has shown poor read and write performance for small files over NFS implementations, and as such we view it unlikely that this policy will change for the index and database stores. The binary database products used in ZCS such as MySQL, Berkeley DB (Sleepycat), and Lucene each have respective risks and warnings with running on NFS. Zimbra will continue to evaluate support for NFS for the message store as customer demand warrants.
When working with Zimbra Support on related issues, the customer must disclose that the backup storage used is NFS.
Note for ZCS deployed on vSphere 4.1 or later with NFS datastores. All Zimbra zimbra storage components encapsulated in VMDKs and sit on NFS datastores is a supported configuration: http://bugzilla.zimbra.com/show_bug.cgi?id=50635