Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Chapter 1, Understanding VERITAS Volume Manager
Online Relayout
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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.
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. The figure, “Example
of Decreasing the Number of Columns in a Volume” on page 37, 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.
Example of Decreasing the Number of Columns in a Volume
Five Columns of Length L Three Columns of Length 5L/3