Managing Serviceguard Extension for SAP on Integrity Linux, December 2005

Understanding Serviceguard Extension for SAP on Integrity Linux
Highly Available NFS
Chapter 1 17
Highly Available NFS
Distributed SAP environments require the Network File System (NFS)
to be highly available. SGeSAP/LX IPF packages can be combined with
the Serviceguard NFS toolkit for Linux to achieve this functionality.
Typically, the SGeSAP/LX IPF database package also provides HA NFS
functionality.
SGeSAP/LX IPF cluster hosts can usually act as HA NFS servers and as
NFS clients that access these server's filesystems. The cross-mounting
approach is taken to achieve this. The logical volumes that contain the
HA NFS filesystems are mounted below a specific directory, usually
called /export. They are accessed via a different path that is linked to a
location below /import, which is monitored by an automounter instance
that provides the linkage between corresponding /export and /import
directories.
This setup allows NFS servers to be failed to NFS client hosts without
getting into trouble with busy mountpoints for the disk devices. It also
avoids adding static mounts to HA NFS filesystems, which might
interfer machine reboots if HA NFS is not running during reboot time.
NOTE Database datafiles need to be treated differently to avoid measurable
performance impacts and data inconsistencies.