Veritas Storage Foundation 5.0 Cluster File System Administration Guide Extracts for HP Serviceguard Storage Management Suite, Second Edition, May 2008

Cluster Volume Manager Administration
Overview of Cluster Volume Management
Chapter 4
45
• 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:
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.
Table 4-3 Behavior of Master Node for Different Failure Policies
Type of I/O
Failure
Leave
(dgfailpolicy=leave)
Disable
(dgfailpolicy=dgdis
able)
The master
node loses
access to all
copies of the
logs.
The master node panics with the
message “klog update failed” for a failed
kernel-initiated transaction, or “cvm
config update failed” for a failed
user-initiated transaction.
The master node
disables the disk
group.