Serviceguard Extended Distance Cluster (EDC) with VxVM/CVM Mirroring on HP-UX, May 2008

Detach policy and Disk Group Failure policy

There are two policies that control the behavior following I/O errors or failures. These are the detach

policy and the disk group failure policy.

The detach policy has two possible settings:

• Global—This is the default policy. When the detach policy is set to global, a plex will be detached

from a volume on a cluster-wide basis if a CVM slave node experiences an I/O error on that plex.

• Local—This policy was introduced in VxVM 3.2 and is currently not supported with VxVM/CVM

5.0, if the site-awareness feature is being used. If the detach policy is set to local, an I/O error on a

plex will not cause the plex to be detached cluster wide. Only the node which experienced the I/O

error will lose access to the volume.

The disk group failure policy applies when the CVM master node loses access to all the copies of the

configuration database and logs and has two possible settings:

• Disable—This is the default policy. When the disk group failure policy is set to disable, the disk

group will be disabled cluster wide if the CVM master node loses access to all copies of the

configuration database and logs. As a result, all cluster nodes will lose access to the disk group.

• Leave—This mode was introduced with VxVM/CVM 4.1. With the disk group failure policy set to

leave, if the CVM master node loses access to all copies of the configuration database and logs,

the CVM master node will be forced to leave the cluster (panic). This will trigger a cluster

reformation, causing a new CVM master to be selected.

The information documented in this white paper is based on tests that were performed using the

default settings for the detach and disk group failure policies—these settings were recommended by

Symantec. Further details of these policies can be found in the “VERITAS Volume Manager

Administrator’s Guides” referred to in the “