Striping at Vxvm can still improve performance, but I wouldn't go beyond 4 colums and you should ensure that no disks in one column are in the same raid set (i.e shared the same spindles) as another column, otherwise the striping will not improve performance and could reduce it. If you are not sure how the back-end is configured then best to configure as concat, rather than stripe and modern arrays perform so well, that the extra benefit of striping at vxvm level will probably not be noticed unless you are writing several GB in a very short time (like a database import).
If you can delete the existing volume (lose all data in /prod01p) then this is the easiest:
umount /prod01p
vxassist -g vgbackup remove volume vol_prod01p
vxassist -g vgbackup make vol_prod01p 4096g ncol=4
mkfs -Fvxfs /dev/vx/rdsk/vgbackup/vol_prod01p
mount /dev/vx/dsk/vgbackup/vol_prod01p /prod01p
This will create a 4TB striped column with 4 columns or if you omit the ncol=4, will create a concat (non-striped volume).
You will require 4 LUNs at a time to increase the striped volume, or a concat volume can be increased one LUN at a time.
Mike