Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Figure 1-6
VM disk example
disk01
VM disk
Physical disk
devname
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 29.
Figure 1-7 shows disk01-01 is the name of the first subdisk on the VM disk named
disk01.
Figure 1-7
Subdisk example
Subdisk
VM disk with one subdisk
disk01
disk01-01
disk01-01
A VM disk can contain multiple subdisks, but subdisks cannot overlap or share
the same portions of a VM disk. To ensure integrity, VxVM rejects any commands
that try to create overlapping subdisks.
Figure 1-8 shows a VM disk with three subdisks, which are assigned from one
physical disk.
31Understanding Veritas Volume Manager
How VxVM handles storage management