Managing Serviceguard Extension for SAP Version B.05.10, December 2012

Each file system that gets added to a system by SAP installation routines must be classified and a
decision has to be made:
• Whether the file system needs to be kept as a local copy on internal disks of each node of
the cluster.
• Whether the file system needs to be shared on a SAN storage device to allow failover and
exclusive activation.
• Whether the file system needs to provide shared access to more than one node of the cluster
at the same time.
NOTE: SGeSAP packages and service monitors require SAP tools. Patching the SAP kernel
sometimes also patches SAP tools. Depending on what SAP changed, this might introduce additional
dependencies on shared libraries that weren't required before the patch. Depending on the
SHLIB_PATH settings of the root user, it may not be possible for SGeSAP to execute the SAP tools
after applying the patch. The introduced additional libraries are not found. Creating local copies
of the complete central executable directory prevents this issue.
The following sections detail the three different storage options.
Option 1: SGeSAP NFS Cluster
With this storage setup, SGeSAP makes extensive use of exclusive volume group activation.
Concurrent shared access is provided via NFS services. Automounter and cross-mounting concepts
are used in order to allow each node of the cluster to switch roles between serving and using NFS
shares. It is possible to access the NFS file systems from servers outside of the cluster that is an
intrinsic part of many SAP configurations.
Common Directories that are Kept Local
The following common directories and their files are kept local on each node of the cluster:
• /home/<sid>adm — the home directory of the SAP system administrator with node specific
startup log files.
• /usr/sap/<SID>/SYS/exe/run — the directory that holds a local copy of all SAP instance
executables, libraries, and tools (optional for kernel 7.x and higher).
• /usr/sap/tmp — the directory where the SAP operating system collector keeps monitoring
data of the local operating system.
• /usr/sap/hostctrl — the directory where SAP control services for the local host are kept
(kernel 7.x and higher).
• /etc/cmcluster — the directory where Serviceguard keeps its legacy configuration files
and the node specific package runtime directories.
• Depending on database vendor and version, it might be required to keep local database
client software. Details can be found in the database sections below.
Part of the content of the local group of directories must be synchronized manually between all
nodes of the cluster. Serviceguard provides a tool cmcp(1m) that allows easy replication of a file
to all cluster nodes.
SAP instance (startup) profile names contain either local hostnames or virtual hostnames. SGeSAP
will always prefer profiles that use local hostnames to allow individual startup profiles for each
host, which might be useful if the failover hardware differs in size.
In clustered SAP environments prior to 7.x releases, local executables must be installed. Local
executables help to prevent several causes for package startup or package shutdown hangs due
to the unavailability of the centralized executable directory. Availability of executables delivered
with packaged SAP components is mandatory for proper package operation. Experience has
SAP Instance Storage Considerations 31