Managing Serviceguard 13th Edition, February 2007

Understanding Serviceguard Software Components
Volume Managers for Data Storage
Chapter 3124
CVM can be used in clusters that:
• run applications that require fast disk group activation after package
failover;
• require storage activation on more than one node at a time, for
example to perform a backup from one node while a package using
the volume is active on another node. In this case, the package using
the disk group would have the disk group active in exclusive write
mode while the node that is doing the backup would have the disk
group active in shared read mode;
• run applications, such as Oracle RAC, that require concurrent
storage read/write access between multiple nodes.
Heartbeat is configured differently for CVM 3.5 and 4.1. See “Redundant
Heartbeat Subnet Required” on page 124.
Shared storage devices must be connected to all nodes in the cluster,
whether or not the node accesses data on the device.
Cluster Startup Time with CVM
All shared disk groups (DGs) are imported when the system multi-node’s
control script starts up CVM. Depending on the number of DGs, the
number of nodes and the configuration of these (number of disks,
volumes, etc.) this can take some time (current timeout value for this
package is 3 minutes but for larger configurations this may have to be
increased). Any failover package that uses a CVM DG will not start until
the system multi-node package is up. Note that this delay does not affect
package failover time; it is a one-time overhead cost at cluster startup.
Propagation of Disk Groups with CVM
CVM disk groups are created on one cluster node known as the CVM
master node. CVM verifies that each node can see each disk and will not
allow invalid DGs to be created.
Redundant Heartbeat Subnet Required
HP recommends that you configure all subnets that connect cluster
nodes as heartbeat networks; this increases protection against multiple
faults at no additional cost.
Heartbeat configurations are configured differently for CVM 3.5 and 4.1.
You can create redundancy in the following ways: