Hi,
Did you check here : http://failprevent.wordpress.com/2012/02/17/esx-cli-create-vmfs-and-datastore-on-backend-storage/
1- Create a Partition Table
~ # fdisk /vmfs/devices/disks/naa.600140597d318d3dc4dfd3d6ad84f3d8
m: menu
p: print current partition table
-> It should be empty
n: new partition
-> follow wizzard
t: set partition type to VMFS
-> fb
w: write partition table & exit
2 - Create a VMFS datastore
~ # vmkfstools -C vmfs5 -S datastorename /vmfs/devices/disks/naa.600140597d318d3dc4dfd3d6ad84f3d8\:1
I hope it help.
Regards,
Julien.