First I did an fdisk, created a primary partition that took up the whole disk. It was type "fb"
Command (m for help): p
Disk /dev/sdb: 640.1 GB, 640136773632 bytes 255 heads, 63 sectors/track, 77825 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 77825 625129281 fb Unknown Command (m for help): q
Then to put VMFS3 on it,
vmkfstools -C vmfs3 -S local vmhba1:0:0:1