Filter
Top Products
402 Administering cluster functionality
Overview of cluster volume management
cluster-shareable disk group is available as long as at least one node is active in
the cluster. The failure of a cluster node does not affect access by the remaining
active nodes. Regardless of which node accesses a cluster-shareable disk group,
the configuration of the disk group looks the same.
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 a distributed lock manager, for example).
Activation modes of 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 detail in the table “Activation modes for
shared disk groups.”
Note: The default activation mode for shared disk groups is off (inactive).
Special uses of clusters, such as high availability (HA) applications and off-host
backup, can use disk group activation to explicitly control volume access from
different nodes in the cluster.
Table 13-1 Activation modes for shared disk groups
Activation mode Description
exclusivewrite (ew) The node has exclusive write access to the disk group. No
other node can activate the disk group for write access.
readonly (ro) 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.
sharedread (sr) 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.