Fencing drives are formatted and controlled by Veritas File system within VCS. You can get away with setting up one fencing drive, however three fencing drives for HA are strongly recommended by Symantec. You cannot do it with Linux LVM. That sucks.
On the side note, VCS only supports Linux LVM in I/O single-multipathing node. For I/O multipathing, Veritas Storage Foundation, VxFS are required.
You could find more info in VCS implementation guides found on Symantec Website.
Cheers,
