HP UX Serviceguard Storage Management Software manual # cfsdgadm display

Cluster Volume Manager Administration

Overview of Cluster Volume Management

•exclusive-write

•read-only

•shared-read

•shared-write

•off

To view the activation mode setting for each of your shared disk groups, enter:

#cfsdgadm display

When a shared disk group is created or imported, it is activated in the specified mode. When a node joins the cluster, all shared disk groups accessible from the node are activated in the specified mode.

If the defaults file is edited while the vxconfigd daemon is already running, the vxconfigd process must be restarted for the changes in the defaults file to take effect.

If the default activation mode is anything other than off, an activation following a cluster join, or an activation following a disk group creation (or import) will fail, if another node in the cluster has activated the disk group in a conflicting mode.

To display the activation mode for a shared disk group, use the vxdg list diskgroup command.

You can also use the vxdg command to change the activation mode on a shared disk group.

Connectivity Policy of Shared Disk Groups

The nodes in a cluster must agree on the status of a disk, or a connectivity policy setting will determine the disk status. If one node cannot write to a particular disk, all nodes must stop accessing that disk before the results of the write operation are returned to the caller. If a node cannot contact a disk, it must contact another node to check on the disk’s status. If a disk fails, the nodes will agree to detach the disk, because no node can access it. If a disk does not fail, but the access paths to that disk from some of the nodes in the cluster fail, the nodes in the cluster will not be able to agree on the status of the disk. In this case, one of the following connectivity policies will be applied:

•Under the global connectivity policy, the detach occurs cluster-wide (globally) if any node in the cluster reports a disk connectivity failure. This is the default connectivity policy.

•Under the local connectivity policy, if disk connectivity fails, the failure is confined to the particular nodes that see the failure. An attempt is made to communicate with all nodes in the cluster to determine the usability of the disks. If all nodes report a problem with the disks, a cluster-wide detach occurs.

The vxdg command is used to set the disk detach and disk group failure policy. The dgfailpolicy attribute sets the disk group failure policy in the case that the master node loses connectivity to the configuration and to the log copies within a shared disk group. This attribute requires that the disk group version is 120 or greater. The following policies are supported:

•dgdisable—The master node disables the diskgroup for all user or kernel initiated transactions. First write and final close fail. This is the default policy.

44 Chapter 4