3.5.1 Matrix Server Administration Guide

Chapter 8: Configure MxFS-Linux 135

One or Many Export Groups?

In the typical configuration, a single Export Group associated with

multiple Virtual NFS Services is recommended.

High Availability and Failover Support

MxFS-Linux provides high availability for the exported PSFS filesystems.

To ensure that the filesystems are always available, MxFS-Linux provides

a global NFS monitor for the system as well as a high-availability monitor

for each Export Group. The global NFS monitor periodically checks the

NFS service and the MxFS-Linux processes on each node. On each server

configured for the Export Group, the Export Group monitor periodically

checks the exported filesystems to determine if they are mounted.

If a failure occurs on the server to which NFS clients are connected or the

server loses access to the PSFS filesystem (for example, because of a SAN

problem), the appropriate monitor probe will report the failure. The

Virtual NFS Services active on that server are then failed over (redirected)

to a backup server. Failover is transparent to the NFS clients; their access

to the exported filesystems continues after a brief pause.

Caveats Regarding Export Groups

Before creating an Export Group, you should be aware of the following:

• Although you can configure multiple Export Group files, with each

group having its own set of export records, all of the export records

are ultimately merged into a single /etc/exports file that is

automatically installed on each node in the cluster. Because an export

can be included in more than one Export Group, the /etc/exports file

can contain multiple records referring to the same filesystem path to

be exported. If these duplicate records specify different export

options, it is indeterminate which options the NFS service will

assume. It is therefore recommended that any given filesystem subtree

be exported by at most one Export Group.

• Although an Export Group can specify that only certain nodes can

export its filesystems, the contents of the Export Group are available

via the /etc/exports file on every node in the cluster. This means that

users can access the exported filesystems from nodes where the

Export Group is not defined by connecting via the physical address of