I found it, it's related with the item 510 of the NewsGroup, it's related
to the partitioning of the disks of the array, for reference you can compare
the arrange with one disk used for the system:

with format for an 36Gb disk, the partition #2 shows like this :

2 backup wm 0 - 24619 33.92GB (24620/0/0) 71127180

then, on EACH disk of the array, you need to format the partition #2 to describe
the entire disk

and in the size of the partition, it must says : 71127180b
(71127180 blocks)

I agree, it's a weakness of Veritas VM