User's Guide

Directories that Reside on Shared Disks
Volume groups on SAN shard storage are configured as part of the SGeSAP packages. They can be either:
• instance specific or
• system specific or
• environment specific.
Instance specific volume groups are required by only one SAP instance or one database instance. They
usually get included with exactly the package that is set up for this instance.
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 HA NFS to
provide access for all instances. They shouldn't 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 it is recommended to separate
the environment specific volume groups to a dedicated HA NFS package. This package will be referred to
as sapnfs package. It should remain running all the time, since it is of central importance for the whole setup.
Since sapnfs is just serving networked file systems, there is rarely needed to stop this package at any time.
If environment specific volume groups become part of a database package, there will be a potential
dependency between packages of different SAP Systems. Stopping one SAP System by halting all related
Serviceguard packages will then lead to a lack of necessary NFS resources for otherwise 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 HA NFS mechanisms completely
separate.
A valuable naming convention for most of these shared volume groups is vg<INSTNAME><SID> or
alternatively vg<INSTNAME><SID><INR>. Table 2-2 and Table 2-3 provide an overview of SAP shared
storage and maps them to the component and package type for which they occur.
Table 2-2 Instance Specific Volume Groups for exclusive activation with a package
Device minor
number
VG NameRecommended packagesAccess PointMount Point
jci<SID> (scs<SID>)
jdbjci<SID>
Shared disk/usr/sap/<SID>/SCS<INR>
ci<SID> (ascs<SID>)
dbci<SID>
/usr/sap/<SID>/ASCS<INR>
ers<INR><SID>/usr/sap/<SID>/ERS<INR>
ci<SID>
dbci<SID>
d<INR><SID>
(SAP kernel 7.x)
/usr/sap/<SID>/DVEBMGS<INR>
d<INR><SID>/usr/sap/<SID>/D<INR>
SAP Instance Storage Considerations 23