HP Serviceguard Extension for SAP (SGeSAP) manual Planning the Storage Layout

2 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 in some cases. SGeSAP supports various combinations of providing shared access to file systems in the cluster. The possible storage layout and file system configuration options include:

Each filesystem that gets added by the SAP installation routines needs to be classified and a decision has to be made.

Refer to table 2-1 for more information.

Table 2-1 Option descriptions

Option:	Description
1 - SGeSAP NFS Cluster	optimized to provide maximum flexibility. Following the recommendations given below allows
	for expansion of existing clusters without limitations caused by the 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, it is not required to make changes to already existing file systems. Option 1 is
	recommended for environments that implement clusters with server consolidation if CFS is not
	available.
2 - SGeSAP NFS Idle Standby	optimized to provide maximum simplicity. The option is only feasible for very simple clusters. It
Cluster	needs to be foreseeable that their layout and configuration won't change 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.
3 - SGeSAP CFS Cluster	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 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.

Each filesystem that gets added to a system by SAP installation routines needs to be classified and a decision has to be made:

SAP Instance Storage Considerations 21