Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 5 - Preparing Shared Storage

Cluster Volume Management

The Veritas cluster volume manager (CVM) uses objects for storage management. The two types of objects used by Volume Manager are physical objects and virtual objects.

• Physical objects - Volume Manager uses two physical objects: physical disks and partitions. Partitions are created on the physical disks (on systems that use partitions).
   

• Virtual objects - Volume Manager creates virtual objects, called volumes. Each volume records and retrieves data from one or more physical disks. A volume is a virtual disk device that appears to applications, databases, and file systems as a physical disk. Volumes are also composed of other virtual objects such as 'sub-disks' and 'plexes'. These are used to change volume configuration features such as concatenation, mirroring, and striping. Volumes and their virtual components are called virtual objects.

Volume management involves using physical disks or LUNS to create disk groups. These disks are combined to create volumes with a layout or configuration appropriate to their purpose, for example, mirroring or striping, etc. The volumes are flexible objects that can easily be extended or modified. The volume management operations include: