NFS Services Administrator's Guide (B.11.31.02) January 2008

authentication and encryption capabilities. For information on how to share directories in a
secure manner, see “Secure Sharing of Directories ” (page 28).
Client Failover
By using client-side failover, an NFS client can specify redundant servers that are making the
same data available and switch to an alternate server when the current server becomes unavailable.
The filesystems on the current server can become unavailable for the following reasons:
• If the filesystem is connected to a server that crashes
• If the server is overloaded
• If a network fault occurs
A failover occurs when the filesystem is unavailable. The failover is transparent to the user. The
failover can occur at any time without disrupting processes that are running on the client.
Consider the following points before enabling client-side failover:
• The filesystem must be mounted with read-only permissions.
• The filesystems must be identical on all the redundant servers for the failover to occur
successfully. For information on identical filesystems, see “Replicated Filesystems” (page 20).
• A static filesystem or one that is not modified often is used for failover.
• File systems that are mounted using CacheFS are not supported for use with failover.
• If client-side failover is enabled using the command-line option, the listed servers must
support the same version of the NFS protocol. For example, onc21 and onc23 must support
the same version of NFS protocol, either NFSv2, NFSv3, or NFSv4.
For information on how to enable client-side failover, see “Enabling Client-Side Failover”
(page 41).
Replicated Filesystems
A replicated filesystem contains the corresponding directory structures and identical files. A
replica (identical copy) of a filesystem consists of files of the same size and same file type as the
original filesystem.
HP recommends that you create these replicated filesystems using the rdist utility.
The rdist utility enables you to maintain identical copies of files on multiple hosts. It preserves
the owner, group, mode, modification time of files, and updates programs that are running.
Enhanced NFS Logging
The NFS server logging enables an NFS server to provide a record of file operations that are
performed on its filesystems. The record includes information about the file accessed, time of
access, and the users who accessed the files. You can also specify the location of the logs that
contain this information. This feature is useful for sites that make anonymous FTP archives
available to NFS and WebNFS clients.
IPv6 Support
NFS supports filesystem mounting over an IPv4 or an IPv6 address where square brackets enclose
the IPv6 address.
The nsquery feature supports ipnodes lookup request and provides support to lookup IPv6
data in the backend libraries.
20 Introduction