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

4 Planning the Storage Layout
Volume managers are tools that let you create units of disk storage known as storage groups.
Storage groups contain logical volumes for use on single systems and in high availability clusters.
In Serviceguard clusters, package control scripts activate storage groups. Two volume managers
can be used with Serviceguard: the standard Logical Volume Manager (LVM) of HP-UX and the
Veritas Volume Manager (VxVM). SGeSAP can be used with both volume managers. The following
steps describe two standard setups for the LVM volume manager. VxVM setups can be configured
accordingly. A third storage layout option describes a Cluster File System configuration for SGeSAP.
In this case, VxVM must be used and all Application Servers need to run on cluster nodes. Chapter
three explores the concepts and details the implementation steps discussed in this chapter.
Database storage layouts for usage with parallel databases are only briefly described for Oracle
Real Application Clusters. Detailed configuration steps for parallel database technologies are not
covered in this manual. Additional information about SGeSAP and parallel databases is being
released as whitepapers from HP. Refer to the Additional Reading section of the relevant SGeSAP
release notes to verify the availability of whitepapers in this area.
This chapter discusses disk layout for clustered SAP components and database components of
several vendors on a conception level. It is divided into two main sections:
• SAP Instance Storage Considerations
• Database Instance Storage Considerations
SAP Instance Storage Considerations
In general, it is important to stay as close as possible to the original layout intended by SAP. But,
certain cluster-specific considerations might suggest a slightly different approach. SGeSAP supports
various combinations of providing shared access to file systems in the cluster.
Table 3 Option descriptions
DescriptionOption
Optimized to provide maximum flexibility. Following the recommendations given below
allows for expansion of existing clusters without limitations caused by the cluster.
1. SGeSAP NFS Cluster
Another important design goal of SGeSAP option 1 is that a redesign of the storage
layout is not imperative when adding additional SAP components later on. Effective
change management is an important aspect for production environments. The disk
layout needs to be as flexible as possible to allow growth to be done by just adding
storage for newly added components. If the design is planned carefully at the
beginning, making changes to already existing file systems is not required. Option 1
is recommended for environments that implement clusters with server consolidation if
CFS is not available.
Optimized to provide maximum simplicity. The option is only feasible for very simple
clusters. It needs to be foreseeable that the layout and configuration won't change
2. SGeSAP NFS Idle Standby
Cluster
over time. It comes with the disadvantage of being locked into restricted configurations
with a single SAP System and idle standby nodes. HP recommends option 1 in case
of uncertainty about potential future layout changes.
Combines maximum flexibility with the convenience of a Cluster File System. It is the
most advanced option. CFS should be used with SAP if available. The HP Serviceguard
3. SGeSAP CFS Cluster
Cluster File System requires a set of multi-node packages. The number of packages
varies with the number of disk groups and mountpoints for Cluster File Systems. This
can be a limiting factor for highly consolidated SGeSAP environments.
30 Planning the Storage Layout