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

■ If a given disk group spans multiple controllers and has more than one spare
disk, set up the spare disks on different controllers (in case one of the
controllers fails).
■ For a mirrored volume, configure the disk group so that there is at least one
disk that does not already contain a mirror of the volume. This disk should
either be a spare disk with some available space or a regular disk with some
free space and the disk is not excluded from hot-relocation use.
■ For a mirrored and striped volume, configure the disk group so that at least
one disk does not already contain one of the mirrors of the volume or another
subdisk in the striped plex. This disk should either be a spare disk with some
available space or a regular disk with some free space and the disk is not
excluded from hot-relocation use.
■ For a RAID-5 volume, configure the disk group so that at least one disk does
not already contain the RAID-5 plex (or one of its log plexes) of the volume.
This disk should either be a spare disk with some available space or a regular
disk with some free space and the disk is not excluded from hot-relocation
use.
■ If a mirrored volume has a DRL log subdisk as part of its data plex, you cannot
relocate the data plex. Instead, place log subdisks in log plexes that contain
no data.
■ Hot-relocation does not guarantee to preserve the original performance
characteristics or data layout. Examine the locations of newly-relocated
subdisks to determine whether they should be relocated to more suitable disks
to regain the original performance benefits.
■ Although it is possible to build Veritas Volume Manager objects on spare disks,
it is recommended that you use spare disks for hot-relocation only.
See “How hot-relocation works” on page 406.
Accessing volume devices
As soon as a volume has been created and initialized, it is available for use as a
virtual disk partition by the operating system for the creation of a file system, or
by application programs such as relational databases and other data management
software.
Creating a volume in a disk group sets up block and character (raw) device files
that can be used to access the volume:
block device file for volume vol in disk group
dg
/dev/vx/dsk/dg/vol
557Configuring Veritas Volume Manager
Guidelines for configuring storage