User's Guide

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
DescriptionOption:
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.
1 - SGeSAP NFS Cluster
optimized to provide maximum simplicity. The option is only feasible for very simple clusters. It
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.
2 - SGeSAP NFS Idle Standby
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.
3 - SGeSAP CFS Cluster
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