Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

503Configuring Veritas Volume Manager
Guidelines for configuring storage
■ After hot-relocation occurs, designate one or more additional disks as spares to
augment the spare space. Some of the original spare space may be occupied by
relocated subdisks.
■ 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 (using
vxmake or the VEA interface), it is recommended that you use spare disks for hot-
relocation only.
See “Administering hot-relocation” on page 369 for more information.
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:
/dev/vx/dsk/diskgroup/volumeblock device file for volume
/dev/vx/rdsk/diskgroup/volumecharacter device file for volume