Veritas Volume Manager 5.0 Administrator's Guide (September 2006)
395Administering cluster functionality
Overview of cluster volume management
continues to return write errors, as long as one mirror of the volume has an error. The
volume continues to satisfy read requests as long as one good plex is available.
If the reason for the I/O error is corrected and the node is still a member of the cluster, it
can resume performing I/O from/to the volume without affecting the redundancy of the
data.
See “Setting the disk detach policy on a shared disk group” on page 412 for information
on how to use the
vxdg command to set the disk detach policy on a shared disk group.
The table, “Cluster behavior under I/O failure to a mirrored volume for different disk
detach policies,” summarizes the effect on a cluster of I/O failure to the disks in a mirrored
volume:
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
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)
Failure of path to one
disk in a volume for a
single node
Reads fail only if no plexes remain
available to the affected node.
Writes to the volume fail.
The plex is detached, and I/O
from/to the volume continues. An
I/O error is generated if no plexes
remain.
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.