HP Serviceguard Extension for RAC (SGeRAC) manual About Cluster-wide Device Special Files cDSFs

nomenclature. You are not required to migrate to agile addressing when you upgrade to 11i v3, though you should seriously consider its advantages. It is possible, though not a best practice, to have legacy DSFs on some nodes and agile addressing on others—this allows you to migrate the names on different nodes at different times, if necessary.

NOTE: The examples in this document use legacy naming conventions.

About Cluster-wide Device Special Files (cDSFs)

Under agile addressing on HP-UX 11i v3, each device has a unique identifier as seen from a given host; this identifier is reflected in the name of the Device Special File (DSF).

Because DSF names may be duplicated between one host and other, it is possible for different storage devices to have the same name on different nodes in a cluster, and for the same piece of storage to be addressed by different names. Cluster-wide device files (cDSFs), available as of the September 2010 HP-UX Fusion Release, ensure that each storage device used by the cluster has a unique device file name.

IMPORTANT: Check the latest version of the release notes (at the address given in the preface to this manual) for information about Serviceguard support for cDSFs.

HP recommends that you use cDSFs for the storage devices in the cluster because this makes it simpler to deploy and maintain a cluster, and removes a potential source of configuration errors. For more information, see Creating Cluster-wide Device Special Files (cDSFs) in the Managing Serviceguard, Eighteenth Edition manual at www.hp.com/go/hpux-serviceguard-docs—> HP Serviceguard .

Points to Note

•cDSFs can be created for any group of nodes that you specify, provided that Serviceguard A.11.20 is installed on each node.

Normally, the group should comprise the entire cluster.

•cDSFs apply only to shared storage; they will not be generated for local storage, such as root, boot, and swap devices.

•Once you have created cDSFs for the cluster, HP-UX automatically creates new cDSFs when you add shared storage.

•HP recommends that you do not mix cDSFs with persistent (or legacy DSFs) in a volume group, and you cannot use cmpreparestg (1m) on a volume group in which they are mixed.

For more information about cmpreparestg, see About Easy Deployment in the Managing Serviceguard, Nineteenth Edition manual at www.hp.com/go/hpux-serviceguard-docs—> HP Serviceguard .

Where cDSFs Reside

cDSFs reside in two new HP-UX directories, /dev/cdisk for cluster-wide block device files and /dev/rcdisk for cluster-wide character devicefiles. Persistent DSFs that are not cDSFs continue to reside in /dev/disk and /dev/rdisk, and legacy DSFs (DSFs using the naming convention that was standard before HP–UX 11i v3) in /dev/dsk and /dev/rdsk. It is possible that a storage device on an 11i v3 system could be addressed by DSFs of all three types of device — but if you are using cDSFs, you should ensure that you use them exclusively as far as possible.

NOTE: Software that assumes DSFs reside only in /dev/disk and /dev/rdisk will not find cDSFs and may not work properly as a result.

34 Serviceguard Configuration for Oracle 10g, 11gR1, or 11gR2 RAC