VERITAS Volume Manager 4.1 Administrator's Guide

Understanding VERITAS Volume Manager
Online Relayout
Chapter 140
The transformation is done by moving one portion of data at a time in the
source layout to the destination layout. Data is copied from the source
volume to the temporary area, and data is removed from the source
volume storage area in portions. The source volume storage area is then
transformed to the new layout, and the data saved in the temporary area
is written back to the new layout. This operation is repeated until all the
storage and data in the source volume has been transformed to the new
layout.
The default size of the temporary area used during the relayout depends
on the size of the volume and the type of relayout. For volumes larger
than 50MB, the amount of temporary space that is required is usually
10% of the size of the volume, from a minimum of 50MB up to a
maximum of 1GB. For volumes smaller than 50MB, the temporary space
required is the same as the size of the volume.
The following error message displays the number of blocks required if
there is insufficient free space available in the disk group for the
temporary area:
tmpsize too small to perform this relayout (nblks minimum required)
You can override the default size used for the temporary area by using
the tmpsize attribute to vxassist. See the vxassist(1M) manual page for
more information.
Additional permanent disk space may be required for the destination
volumes, depending on the type of relayout that you are performing. This
may happen, for example, if you change the number of columns in a
striped volume. The figure, “Example of Decreasing the Number of
Columns in a Volume,”shows how decreasing the number of columns can
require disks to be added to a volume. The size of the volume remains the
same but an extra disk is needed to extend one of the columns.
Figure 1-27 Example of Decreasing the Number of Columns in a Volume
Five Columns Three Columns