MD3000i HOST GROUPS SHARING VDISKS ACROSS MULTIPLE VM VIRTUAL MACHINES

I have the following 3 x dell 2950 running exs 3.5, These run 5 VMWARE virtual machines "call these vm1-5".All the machines exist on a VDisk created on an MD3000i.The md3000i is split into 3 vdisks , 1 for the Virtual machine env (vmenv), 1 for application data "appdata" ie exchange 2007 and the 3rd for office data."offdata"

I created the host groups for each of my data areas and created and linked the relevant Vdisks. I installed the relevant initiator software onto Vm1-5 , I then attached the appdata vdisk to VM1. No problems so far Vm1 can see and write to Vdisk appdata..all hosted in a virtual Vmware env Great It all goes pearshape from now on.I now want to attach as a shared host vdisk appdata to VM2 "this being the main application server. Iscsi initiator loaded, Disk identified and new local disk e: appears Super.However any data changes to this disk are not reflected on the the other shared host of this Vdisk this being VM1...similarly any data changes from VM1 to appdata are not seen on the dir ouput from VM2.......So i rebooted both vmservers..on restart both had lost the attached vdisk's...both machines reported the disks as offline.,,,I activated the disks on both machines and checked the data.the disks on both machines now only show the data that was originally reported by vm1 ie all data added,changed etc from VM2 is missing..Almost as if each disk is creating and reporting its own MBR and on reboot picks up the MBR record with the latest timestamp.So my question is am I correct in thinking that shared hosted disks means that two machines can share the same vdisk seen by the vm machine as a local disk and live updates should be apparent across the board..if so i have a config problem and need some help finding it. or Have I totally misunderstood the concept and Vmware and MD3000i does not support the sharing of a vdisk as one volume to be seen by two machines as the same local disk.