Managing Serviceguard Eighteenth Edition, September 2010

CVM 4.1 and later can be used with Veritas Cluster File System (CFS) in Serviceguard.
Several of the HP Serviceguard Storage Management Suite bundles include features
to enable both CVM and CFS.
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.
For heartbeat requirements, see “Redundant Heartbeat Subnets” (page 114).
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 Subnets
HP recommends that you configure all subnets that connect cluster nodes as heartbeat
networks; this increases protection against multiple faults at no additional cost.
For CVM 4.1 and later, the minimum recommended configurations are:
1) dual (multiple) heartbeat networks
2) single heartbeat network with standby LAN card(s)
Comparison of Volume Managers
The following table summarizes the advantages and disadvantages of the volume
managers.
114 Understanding Serviceguard Software Components