Veritas Storage Foundation 5.0.1 Cluster File System Administrator's Guide Extracts for the HP Serviceguard Storage Management Suite on HP-UX 11i v3

NOTE: Applications running on each node can access the data on the VM disks simultaneously.
VxVM does not protect against simultaneous writes to shared volumes by more than one node.
It is assumed that applications control consistency (by using Veritas Storage Foundation Cluster
File System or a distributed lock manager, for example).
Activation Modes for Shared Disk Groups
A shared disk group must be activated on a node in order for the volumes in the disk group to
become accessible for application I/O from that node. The ability of applications to read from,
or to write to, volumes is dictated by the activation mode of a shared disk group. Valid activation
modes for a shared disk group are exclusivewrite, readonly, sharedread, sharedwrite,
and off (inactive). These activation modes are described in Table 2-2: “Activation Modes for
Shared Disk Groups”.
NOTE: The default activation mode for shared disk groups is off (inactive).
Special use clusters, such as high availability (HA) applications and off-host backup, can employ
disk group activation to explicitly control volume access from different nodes in the cluster.
Table 2-2 Activation Modes for Shared Disk Groups
DescriptionActivation Mode
The node has exclusive write access to the disk group. No other node can activate the
disk group for write access.
exclusivewrite
The node has read access to the disk group and denies write access for all other nodes in
the cluster. The node has no write access to the disk group. Attempts to activate a disk
group for either of the write modes on other nodes fail.
readonly
The node has read access to the disk group. The node has no write access to the disk
group, however other nodes can obtain write access.
sharedread
The node has write access to the disk group.
sharedwrite
The node has neither read nor write access to the disk group. Query operations on the
disk group are permitted.
off
The following table summarizes the allowed and conflicting activation modes for shared disk
groups:
Table 2-3 Allowed and conflicting activation modes
Attempt to activate disk group on another node as:Disk group activated in
cluster as:
sharedwritesharedreadreadonlyexclusive- write
FailsSucceedsFailsFails
exclusivewrite
FailsSucceedsSucceedsFails
readonly
SucceedsSucceedsSucceedsSucceeds
sharedread
SucceedsSucceedsFailsFails
sharedwrite
Shared disk groups can be automatically activated in any mode during disk group creation or
during manual or auto-import. To control auto-activation of shared disk groups, the defaults
file /etc/default/vxdg must be created.
The defaults file /etc/default/vxdg must contain the following lines:
enable_activation=true
default_activation_mode=activation-mode
About Veritas Cluster Volume Manager Functionality 21