Managing HP Serviceguard Extension for SAP for Linux, December 2013

System-specific volume groups get accessed from all instances that belong to a particular SAP
System. Environment-specific volume groups get accessed from all instances that belong to all SAP
Systems installed in the whole SAP environment. System and environment-specific volume groups
are set up using NFS to provide access for all instances. They must not be part of a package that
is only dedicated to a single SAP instance if there are several of them. If this package is down,
then other instances would also be impacted. As a rule of thumb, it is a good default to put all
these volume groups into a package that holds the database of the system. These filesystems often
provide tools for database handling that don't require the SAP instance at all.
In consolidated environments with more than one SAP application component, the recommendation
is to separate the environment-specific volume groups to a dedicated NFS package. This package
will be referred to as sapnfs package. It must remain running all the time, since it is of central
importance for the whole setup. Because sapnfs is serving networked file systems, there rarely
is a need to stop this package at any time. If environment-specific volume groups become part of
a database package, there is a potential dependency between packages of different SAP Systems.
Stopping one SAP System by halting all related Serviceguard packages will lead to a lack of
necessary NFS resources for unrelated SAP Systems. The sapnfs package avoids this unpleasant
dependency. It is an option to also move the system-specific volume groups to the sapnfs package.
This can be done to keep NFS mechanisms completely separate.
A valuable naming convention for most of these shared volume groups is vg<INSTNAME> or
vg<INSTNAME><SID> (for example, vgASCSC11). Table 5 (page 40) provides an overview of
SAP shared storage and maps them to the component and package type for which they occur.
Usually, instance specific volume groups can be put into dedicated packages or combined with
packages containing the database. Exceptions are ERS instances, because they need to failover
separately and Gateway (G) or WebDispatcher (W) instances , because there is no database
configure with these.
Modular SGeSAP package names do not have to follow a certain naming convention, but it is
recommended to include instance names (at least instance types) and the SAP SID into the name.
A package containing a database must be indicated this in its name (“DB”).
4.1 SAP Instance storage considerations 39