Serviceguard NFS Toolkit A.11.11.06, A.11.23.05 and A.11.31.03 Administrator's Guide

Limitations
The following is a list of limitations when using Serviceguard NFS Toolkit A.11.23.05 with
Serviceguard A.11.17:
• Serviceguard A.11.17 introduces a new MULTI_NODE package type which is not supported
by Serviceguard NFS Toolkit. The only supported package type is FAILOVER.
• Serviceguard A.11.17 provides a new package configuration file template. The new package
configuration file template introduces the following dependency variables:
— DEPENDENCY_NAME
— DEPENDENCY_CONDITION
— DEPENDENCY_LOCATION
The above parameters are not supported in Serviceguard NFS Toolkit A.11.23.05. By default,
these variables are commented out in the nfs.conf file.
Integrating Support for Cluster File Systems into Serviceguard NFS Toolkit
In a non-CFS implementation, access to a specific file must go through a single NFS server which
can limit scalability and cause a performance bottleneck. With CFS, files and filesystems may be
accessed concurrently from multiple servers. By integrating CFS into a Serviceguard NFS
environment, files and filesystems can be accessed concurrently from multiple highly available
NFS servers to improve performance, scalability, and availability.
Initial Serviceguard NFS Toolkit support for CFS will be limited in scope, specifically for
applications that require file locking across NFS mounts during a failover. For applications that
do not require file locking during a failover, a DNS round-robin scheme or other load balancing
tools may be used to distribute the load evenly between the servers. Additional support will be
phased into future releases.
Overview of Cluster File Systems in Serviceguard NFS Toolkit
Current SG-NFS over VxFS Support
In a Serviceguard environment, a Serviceguard NFS over VxFS (failover) package is defined as
a collection of resources including relocatable IP addresses and logical volume groups (data
disks) associated with NFS services. If the server on which a package is running fails, then
Serviceguard will automatically start the NFS package on the adoptive node. The adoptive node
takes control of the IP addresses and disks and starts the NFS services.
CFS versus Non-CFS Implementation
The Serviceguard A.11.18 release supports CFS which provides data and lock coherency and
allows files and filesystems to be shared and accessed concurrently by multiple servers.
Figure 1–1 shows how files and filesystems are accessed differently in a non-CFS environment
versus a CFS environment. In a non-CFS environment, the highly available filesystems move
from one node to another when there is a failover. The solid lines show which primary node
provides access to which filesystem and the dotted lines show which adoptive node provides
access in the event of a failover. The volumes are exclusively activated only on the server that
currently runs the package, which prevents files and filesystems from being altered concurrently
by multiple nodes. 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.
Integrating Support for Cluster File Systems into Serviceguard NFS Toolkit 11