DB2 and NFS

Storing DB2 database objects is only supported when the remote filesystem is contained on a Network Appliance Filer, IBM iSCSI, or IBM Network Attached Storage. The primary reason for this is due to the fact that these are dedicated devices which provide higher levels of fault tolerance to compensate for where NFS lacks in reliability. For example, when an NFS client writes to an NFS server, the server software will cache the data before physically writing the data to its disk but will return a message to the NFS client indicating that the write was successfully completed. This is done for performance reasons; imagine how slow NFS would be if all NFS clients had to wait for the NFS server to physically write all received data to disk before returning an OK message! It is then easy to see that reliability and data consistency can be serious issues with NFS; if a power failure or other severe interruption occurs after the NFS server software returns an OK message to the NFS client but before it physically writes the data to disk, data inconsistency will arise. The Network Appliance Filer for example, resolves this issue by only caching the data to be written to non-volitile RAM which is recoverable in the event of a power failure.