Administrator's Guide

Cluster File System Architecture

About Veritas Cluster Volume Manager Functionality

Chapter 2

contact a disk, it should contact another node to check on the disk’s status. If the disk

fails, no node can access it and the nodes can agree to detach the disk. If the disk does

not fail, but rather the access paths from some of the nodes fail, the nodes cannot agree

on the status of the disk. Either of the following policies for resolving this type of

discrepancy may be applied:

• Under the global connectivity policy, the detach occurs cluster-wide (globally) if any

node in the cluster reports a disk failure. This is the default policy.

• Under the local connectivity policy, in the event of disks failing, the failures are

confined to the particular nodes that saw the failure. However, this policy is not

highly available because it fails the node even if one of the mirrors is available. Note

that an attempt is made to communicate with all nodes in the cluster to ascertain

the disks’ usability. If all nodes report a problem with the disk, a cluster-wide detach

occurs.

Limitations of Shared Disk Groups

The cluster functionality of VxVM does not support RAID-5 volumes, or task monitoring

for cluster-shareable disk groups. These features can, however, be used in private disk

groups that are attached to specific nodes of a cluster. Online relayout is supported

provided that it does not involve RAID-5 volumes.

The root disk group cannot be made cluster-shareable. It must be private.

Only raw device access may be performed via the cluster functionality of VxVM. It does

not support shared access to file systems in shared volumes unless the appropriate

software, such as the HP Serviceguard Storage Management Suite, is installed and

configured.

If a shared disk group contains unsupported objects, deport it and then re-import the

disk group as private on one of the cluster nodes. Reorganize the volumes into layouts

that are supported for shared disk groups, and then deport and re-import the disk group

as shared.