VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Understanding VERITAS Volume Manager
Online Relayout
Chapter 1 45
• 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 308 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.
• 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.)
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 redundancy by
mirroring any temporary space used. Read and write access to data is
not interrupted during the transformation.
Data is not corrupted if the system fails during a transformation. The
transformation continues after the system is restored and both read and
write access are maintained.
You can reverse the layout transformation process at any time, but the
data may not be returned to the exact previous storage location. Any
existing transformation in the volume must be stopped before doing a
reversal.