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

51Understanding Veritas Volume Manager
Online relayout
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.
As well as the temporary area, space is required for a temporary intermediate volume
when increasing the column length of a striped volume. The amount of space required is
the difference between the column lengths of the target and source volumes. For example,
20GB of temporary additional space is required to relayout a 150GB striped volume with
5 columns of length 30GB as 3 columns of length 50GB. In some cases, the amount of
temporary space that is required is relatively large. For example, a relayout of a 150GB
striped volume with 5 columns as a concatenated volume (with effectively one column)
requires 120GB of space for the intermediate volume.
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. Figure 1-26 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 1-26 Example of decreasing the number of columns in a volume
The following are examples of operations that you can perform using online relayout:
■ Change a RAID-5 volume to a concatenated, striped, or layered volume (remove
parity). See Figure 1-27 for an example. Note that removing parity (shown by the
shaded area) decreases the overall storage space that the volume requires.
Five columns of length L Three columns of length 5L/3