User's Guide

• Whether it needs to be kept as a local copy on internal disks of each node of the cluster.
• Whether it needs to be shared on a SAN storage device to allow failover and exclusive activation.
• Whether it 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 might no longer 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, which 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 in which the SAP operating system collector keeps monitoring data
of the local operating system
• /usr/sap/hostctrl — the directory in which SAP control services for the local host are kept (kernel
7.x and higher)
• /etc/cmcluster — the directory in which Serviceguard keeps its legacy configuration files and the
node specific package runtime directories
• Depending on database vendor and version, it might in addition 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 it is required to install local executables. 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 shown that it is a good practice to create local
copies for all files in the central executable directory. This includes shared libraries delivered by SAP.
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 might no longer 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.
To automatically synchronize local copies of the executables, SAP components deliver the sapcpe mechanism.
With every startup of the instance, sapcpe matches new executables stored centrally with those stored
locally.
22 Planning the Storage Layout