Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Overview of Cluster Volume Management
356 VERITAS Volume Manager Administrator’s Guide
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 is 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.
See “Setting the Disk Group Failure Policy on a Shared Disk Group” on page 377 for
information on how to use the vxdg command to set the failure policy on a shared disk
group.
Guidelines for Choosing Detach and Failure Policies
In most cases it is recommended that you use the global detach policy, and particularly if
any of the following conditions apply:
◆ If you are using the VCS agents that monitor the cluster functionality of VERITAS
Volume Manager, and which are provided with VERITAS Storage Foundation
TM
for
Cluster File System HA and VERITAS Storage Foundation for databases HA. These
agents do not notify VCS about local failures.
Failure of one or more
disks in a volume for all
nodes.
The plex is detached, and I/O
from/to the volume continues. An
I/O error is generated if no plexes
remain.
The plex is detached, and I/O
from/to the volume continues. An
I/O error is generated if no plexes
remain.
Behavior of Master Node for Different Failure Policies
Type of I/O Failure Leave (dgfailpolicy=leave) Disable (dgfailpolicy=dgdisable)
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.
Cluster Behavior Under I/O Failure to a Mirrored Volume for Different Disk Detach Policies
Type of I/O Failure Local (diskdetpolicy=local) Global (diskdetpolicy=global)