Managing Serviceguard 11th Edition, Version A.11.16, Second Printing June 2004

Understanding Serviceguard Software Components
Volume Managers for Data Storage
Chapter 3114
VxVM can be used in clusters that:
• are of any size, up to 16 nodes.
• require a fast cluster startup time.
• do not require shared storage group activation.
• do not have all nodes cabled to all disks.
• need to use RAID 5 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, 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; up to four nodes are supported, but there is no support for
software mirroring, dynamic multipathing (for active/active storage
devices), or numerous other features that require the additional licenses.
The VERITAS Cluster Volume Manager, CVM (B9117AA) is an
enhanced version of the VxVM volume manager that is specifically
designed for cluster use. When installed with the VERITAS Volume
Manager (B9116AA), 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. Cluster information is provided via a special