HP UX Serviceguard Storage Management Software manual Disk Group Failure Policy

Cluster Volume Manager Administration

Overview of Cluster Volume Management

•leave—The master node panics instead of disabling the disk group if a log update fails for a user or kernel initiated transaction (including first write or final close). If the failure to access the log copies is global, all nodes panic in turn as they become the master node.

Disk Group Failure Policy

The local detach policy by itself is insufficient to determine the desired behavior if the master node loses access to all disks that contain copies of the configuration database and logs. In this case, the disk group is disabled. As a result, the other nodes in the cluster also lose access to the volume. In release 4.1, the disk group failure policy was introduced to determine the behavior of the master node in such cases.

This policy has two possible settings as shown in the following table:

Table 4-3	Behavior of Master Node for Different Failure Policies
	Type of I/O	Leave	Disable
			(dgfailpolicy=dgdis
	Failure	(dgfailpolicy=leave)
			able)
	The master	The master node panics with the	The master node
	node loses	message “klog update failed” for a failed	disables the disk
	access to all	kernel-initiated transaction, or “cvm	group.
	copies of the	config update failed” for a failed
	logs.	user-initiated transaction.

The behavior of the master node under the disk group failure policy is independent of the setting of the disk detach policy. If the disk group failure policy is set to leave, all nodes panic in the unlikely case that none of them can access the log copies.

	Limitations of Shared Disk Groups
NOTE	The boot disk group (usually aliased as bootdg) cannot be made cluster-shareable. It
	must be private.
	Only raw device access can 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.
	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.
	If you have RAID-5 volumes in a private disk group that you wish to make shareable,
	you must first relayout the volumes as a supported volume type such as stripe-mirror or
	mirror-stripe. Online relayout is supported provided that it does not involve RAID-5
	volumes.
	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.

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