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

53Understanding Veritas Volume Manager
Online relayout
For details of how to perform online relayout operations, see “Performing online relayout”
on page 286. For information about the relayout transformations that are possible, see
“Permitted relayout transformations” on page 287.
Limitations of online relayout
Note the following limitations of online relayout:
■ Log plexes cannot be transformed.
■ Volume snapshots cannot be taken when there is an online relayout operation running
on the volume.
■ Online relayout cannot create a non-layered mirrored volume in a single step. It
always creates a layered mirrored volume even if you specify a non-layered mirrored
layout, such as mirror-stripe or mirror-concat. Use the
vxassist
convert command to turn the layered mirrored volume that results from a relayout
into a non-layered volume. See “Converting between layered and non-layered
volumes” on page 292 for more information.
■ Online relayout can be used only with volumes that have been created using the
vxassist command or the Veritas Enterprise Administrator (VEA).
■ The usual restrictions apply for the minimum number of physical disks that are
required to create the destination layout. For example, mirrored volumes require at
least as many disks as mirrors, striped and RAID-5 volumes require at least as many
disks as columns, and striped-mirror volumes require at least as many disks as
columns multiplied by mirrors.
■ To be eligible for layout transformation, the plexes in a mirrored volume must have
identical stripe widths and numbers of columns. Relayout is not possible unless you
make the layouts of the individual plexes identical.
■ Online relayout involving RAID-5 volumes is not supported for shareable disk
groups in a cluster environment.
■ Online relayout cannot transform sparse plexes, nor can it make any plex sparse. (A
sparse plex is not the same size as the volume, or has regions that are not mapped to
any subdisk.)
■ The number of mirrors in a mirrored volume cannot be changed using relayout.
■ Only one relayout may be applied to a volume at a time.
Transformation characteristics
Transformation of data from one layout to another involves rearrangement of data in the
existing layout to the new layout. During the transformation, online relayout retains data