Managing Serviceguard Extension for SAP, December 2007

Planning the Storage Layout
SAP Instance Storage Considerations
Chapter 252
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:
• /etc/cmcluster—the directory in which Serviceguard keeps its
configuration files and the node specific package runtime directories
• /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
• /usr/sap/tmp—the directory in which the SAP operating system
collector keeps monitoring data of the local operating system
• 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.
Several SAP ABAP components install a startup script called
startsap_<local_hostname>_<id> into the home directory of
<SID>adm. These scripts internally refer to a startup profile of the
instance. With a non-shared home directory it is possible to change this
reference to point to individual startup profiles for each host. This allows
individual instance configurations for nodes that have a failover
hardware that differs in size. Netweaver ABAP components allow calling
a generic startsap script and providing a parameter that specifies the
local hostname or even a virtual IP address. If you use a virtual IP
address, you can’t provide individual configuration files.