Managing Serviceguard 12th Edition, March 2006

Understanding Serviceguard Software Components
Volume Managers for Data Storage
Chapter 3 119
• require a fast cluster startup time.
• do not require shared storage group activation. (required with CFS)
• do not have all nodes cabled to all disks. (required with CFS)
• need to use software RAID mirroring or striped mirroring.
• have multiple heartbeat subnets configured.
Propagation of Disk Groups in VxVM
With VxVM, a disk group can be created on any node, with the cluster up
or not. The user then needs to go to each node and validate that disk
group by trying to import it. Thus, although there are more steps
required for propagating disk groups with VxVM than with CVM (see
Cluster Volume Manager, CVM, below), you have the freedom to create
the disk group from any node.
Package Startup Time with VxVM
With VxVM, each disk group is imported by the package control script
that uses the disk group. This means that cluster startup time is not
affected, but individual package startup time might be increased because
VxVM imports the disk group at the time the package starts up.
VERITAS Cluster Volume Manager (CVM)
You may choose to configure cluster storage with the VERITAS Cluster
Volume Manager (CVM) instead of the Volume Manager (VxVM). The
Base-VXVM provides some basic cluster features when Serviceguard is
installed, but there is no support for software mirroring, dynamic
multipathing (for active/active storage devices), or numerous other
features that require the additional licenses.
VxVM supports up to 16 nodes, CVM supports up to 8 nodes, and CFS
supports up to 4 nodes.
VxVM 4.1 (B9116BA), CVM (VERITAS Cluster Volume Manager) 3.5
(B9117AA) and CVM 4.1 (B9117BA) are an enhanced versions of the
VxVM volume manager that is specifically designed for cluster use.
When installed with the VERITAS Volume Manager, the CVM add-on
product provides most of the enhanced VxVM features in a clustered
environment. CVM is truly cluster-aware, obtaining information about
cluster membership from Serviceguard directly.