HP Veritas Volume Manager 5.0 -UX 11i v3 manual Subdisks

Understanding Veritas Volume Manager

How VxVM handles storage management

29

Figure 1-6 VM disk example

disk01

VM disk

devname

Physical disk

Subdisks

A subdisk is a set of contiguous disk blocks. A block is a unit of space on the disk. VxVM allocates disk space using subdisks. A VM disk can be divided into one or more subdisks. Each subdisk represents a specific portion of a VM disk, which is mapped to a specific region of a physical disk.

The default name for a VM disk is diskgroup## and the default name for a subdisk is diskgroup##-##, where diskgroup is the name of the disk group to which the disk belongs (see “Disk groups” on page 28).

In Figure 1-7, disk01-01is the name of the first subdisk on the VM disk named disk01.

Figure 1-7 Subdisk example

disk01-01

Subdisk

disk01-01

disk01

VM disk with one subdisk

A VM disk can contain multiple subdisks, but subdisks cannot overlap or share the same portions of a VM disk. Figure 1-8shows a VM disk with three subdisks. (The VM disk is assigned to one physical disk.)