Any disk to be managed by Volume Manager should have two free
partitions and a small amount of free space (1024 sectors).
The free space should be at the beginning or end of the disk and should not
belong to a partition.
This space is used for storing disk group configurations and a
disk label that ensures that the Volume Manager can identify the disk, even
if it is moved to a different address or controller.
It is also used to keep track of disk configuration and to ensure
correct recovery.
The Volume Manager allocates approximately 1024 sectors (512K) from each
disk for the disk group configurations and the disk label.
This space is sufficient to handle normal disk group configurations for up
to approximately 20 disks.
The boot (root) disk is a special case; if no other space is
available, the Volume Manager will attempt to allocate space usually
reserved for swap by shrinking the swap slice.
This process is known as swap relocation and, if necessary, will happen
automatically during root disk encapsulation.
NOTE:
Although it is possible to put disks with no free space under Volume
Manager control, this should only be used as a migration strategy because
many VxVM capabilities based on disk identity are available only for
disks with the required free space.
See
vxdisk(1M)
for information about the nopriv disk type.