VERITAS Volume Manager 4.1 Administrator's Guide

Understanding VERITAS Volume Manager
How VxVM Handles Storage Management
Chapter 114
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 disk## (such as disk01) and the
default name for a subdisk is disk##-##. In the figure, “Subdisk
Example,”, disk01-01 is the name of the first subdisk on the VM disk
named disk01.
Figure 1-7 Subdisk Example
A VM disk can contain multiple subdisks, but subdisks cannot overlap or
share the same portions of a VM disk. Figure 1-8, “Example of Three
Subdisks Assigned to One VM Disk,” shows a VM disk with three
subdisks. The VM disk is assigned to one physical disk.
Figure 1-8 Example of Three Subdisks Assigned to One VM Disk
Any VM disk space that is not part of a subdisk is free space. You can use
free space to create new subdisks.
VxVM release 3.0 or higher supports the concept of layered volumes in
which subdisks can contain volumes. For more information, see “Layered
Volumes” on page 36.
SubdiskVM Disk with One Subdisk
disk01-01 disk01-01
disk01
VM DiskPhysical Disk Subdisks
devname
disk01
disk01-01
disk01-02
disk01-03
disk01-01
disk01-02
disk01-03