Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

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, any action
that would result in an update to log/config copy will also fail from the other
nodes in the cluster. In release 4.1, the disk group failure policy is introduced to
determine the behavior of the master node in such cases.
Table 13-4 shows how the behavior of the master node changes according to the
setting of the failure policy.
Table 13-4
Behavior of master node for different failure policies
Disable
(dgfailpolicy=
dgdisable)
Leave
(dgfailpolicy=
leave)
Type of I/O
failure
The master node disables the disk
group.
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.
Master node loses
access to all copies
of the logs.
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.
The vxdg command can be used to set the failure policy on a shared disk group.
See “Setting the disk group failure policy on a shared disk group” on page 458.
Guidelines for failure policies
If you have a critical disk group that you do not want to become disabled in the
case that the master node loses access to the copies of the logs, set the disk group
failure policy to leave. This prevents I/O failure on the master node disabling the
disk group. However, critical applications running on the master node fail if they
lose access to the other shared disk groups. In such a case, it may be preferable
to set the policy to dgdisable, and to allow the disk group to be disabled.
The default settings for the detach and failure policies are global and dgdisable
respectively. You can use the vxdg command to change both the detach and failure
policies on a shared disk group, as shown in this example:
435Administering cluster functionality (CVM)
Overview of clustering