Serviceguard NFS Toolkit A.11.11.06, A.11.23.05 and A.11.31.08 Administrator's Guide (October 2011)

The Serviceguard NFS package control scripts ensure that upon package failure or shutdown the
storage is made inaccessible on the node where the package failed or was halted.
Figure 1 CFS versus Non-CFS (VxFS) Implementation
In a Serviceguard CFS environment, files and filesystems are concurrently accessible on multiple
nodes. When a package fails over, the adoptive systems do not have to mount the disks from the
failed system because they are already mounted. There is a new multi-node package that runs on
each server in the cluster and exports all the cluster filesystems. The exported filesystems do not
have to be reexported when a package fails over. These factors may reduce failover time.
The files and filesystems can be shared and accessed concurrently within the cluster. However, file
sharing and access from outside the cluster will still require NFS — client systems which are not
members of the CFS cluster will use NFS to access the shared filesystems.
Cross mounting (with nfs_xmnt script) is not needed since you can use CFS to share files and
filesystems within the cluster.
Figures 1–2 and 1–3 also show how files and filesystems are accessed differently in a CFS
environment versus a non-CFS environment. In a non-CFS environment, clients must access the
server which exports a specific filesystem. In a CFS environment, clients can access the cluster via
a load balancer or another mechanism such as a DNS round-robin scheme (represented by the
cloud in Figure 3.) Each NFS client can be directed to the server which currently has the most
capacity available. This approach has a limitation that clients are bound to a particular NFS server
when they issue the mount command.
NOTE: The implementation of a load balancer or DNS round-robin scheme is optional and is
beyond the scope of this publication. For more information about DNS round-robin addressing
refer to the BIND Name Service Overview section in the HP-US IP Address and Client Administrator's
Guide.
Overview of Cluster File Systems in Serviceguard NFS Toolkit 11