Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

■ Any changes on the master node are automatically coordinated and propagated
to the slave nodes in the cluster.
■ Any failures that require a configuration change must be sent to the master
node so that they can be resolved correctly.
■ As the master node resolves failures, all the slave nodes are correctly updated.
This ensures that all nodes have the same view of the configuration.
The practical implication of this design is that I/O failure on any node results in
the configuration of all nodes being changed. This is known as the global detach
policy. However, in some cases, it is not desirable to have all nodes react in this
way to I/O failure. To address this, an alternate way of responding to I/O failures,
known as the local detach policy, was introduced.
The local detach policy is intended for use with shared mirrored volumes in a
cluster. This policy prevents I/O failure on a single slave node from causing a plex
to be detached. This would require the plex to be resynchronized when it is
subsequently reattached. The local detach policy is available for disk groups that
have a version number of 70 or greater.
For small mirrored volumes, non-mirrored volumes, volumes that use hardware
mirrors, and volumes in private disk groups, there is no benefit in configuring
the local detach policy. In most cases, it is recommended that you use the default
global detach policy.
In the event of the master node losing access to all the disks containing log/config
copies, the disk group failure policy is triggered. At this point no plexes can be
detached, as this requires access to the log/config copies, no configuration changes
to the diskgroup can be made, and any action requiring the kernel to write to the
klog (first open, last close, mark dirty etc) will fail. If this happened in releases
prior to 4.1, the master node always disabled the disk group. Release 4.1 introduces
the disk group failure policy, which allows you to change this behavior for critical
disk groups. This policy is only available for disk groups that have a version
number of 120 or greater.
See “Global detach policy” on page 460.
See “Local detach policy ” on page 460.
See “Disk group failure policy” on page 461.
See “Guidelines for failure policies” on page 462.
459Administering cluster functionality
Overview of cluster volume management