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407Administering cluster functionality
Overview of cluster volume management
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 426
for information on how to use the
vxdg command to set the failure policy on a
shared disk group.
Failure of paths to all
disks in a volume for a
single node
I/O fails for the affected node. The plex is detached, and I/O
from/to the volume continues.
An I/O error is generated if no
plexes remain.
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.
Table 13-4 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.
Table 13-3 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)