NFS replication and global namespace

The NFS version 4 (NFSv4) protocol provides functions that allows you, as the system administrator, to distribute data across multiple servers in a way that is transparent to the users of that data.

You can use two features provided beginning with AIX 5L Version 5.3 with the 5300-03 Recommended Maintenance package. The first is a global namespace feature called a referral. The second feature is a means of specifying locations where copies of data can be found, which is called a replica.

A referral is a special object you can create in the namespace of a server to which location information is attached. The server uses NFSv4 protocol features to redirect clients to the server specified in the location information. The referral forms a building block for integrating data on multiple NFS servers into a single file namespace tree that referral-aware NFSv4 clients can navigate.

A replica is a copy of a file system on one NFS server that has been placed on several other NFS servers (or at an alternate location, such as a different disk on the same server). If a given replica location in use by a replica-aware NFSv4 client becomes unavailable, then the client will switch to another available replica. For more information about replicas, refer to NFS replicas.