Managing Serviceguard Extension for SAP on Integrity Linux, December 2005

Understanding Serviceguard Extension for SAP on Integrity Linux
Planning the LVM Layout for Clustered SAP Environments
Chapter 1 19
Planning the LVM Layout for Clustered SAP
Environments
This section provides a general discussion of the SGeSAP for Integrity
Linux cluster directory and volume group layout. Depending upon the
particular setup, the following groups of filesystems need special
treatment:
•SAP LVM Layout
• Oracle LVM Layout
•SAPDB LVM Layout
• SGeSAP/LX IPF Filestructure
General information about the setup of the shared storage using LVM
can be found in the Managing Serviceguard for Linux manual. Please
refer to this documentation for the details about settings up LVM,
multipathing and RAID devices for shared storage.
Logical volumes that reside on shared disks are only available on a host
if the package they belong to is running. Serviceguard switches them to
another node with the package. Changing shared disk directory files on
any host of the cluster affects the whole cluster. This might be beneficial,
because it keeps the cluster nodes consistent. But it comes with the
drawback that administration mistakes will immediately impact the
whole setup.
Keeping files local on host internal disks allows access even if the cluster
packages are down. The disadvantage here is, that additional diskspace
is needed on each host to keep a copy in opposition to a shared disk
approach where only space for one copy is needed.
The decision which logical volumes should reside on shared disks and
which of them should be kept as a local copy needs to be taken
individually and should carefully balance the advantages and
disadvantages.
< … > brackets are used to refer to placeholders. They need to be
replaced by the corresponding values of the real implementation setup.
Important placeholders that are used throughout this manual include: