Create a shared disk for VMware ESX guests

To create a shared disk between two or more VMs, login into one of your ESX hosts and create a disk image.

cd /vmfs/volumes/#volume-name#/#vm-name#/;
vmkfstools -d thick -a lsilogic -c 50G shareddisk.vmdk;

Add the new hardrive to the guest(s) and select a new SCSI bus (like SCSI 2:0). VMware create a new SCSI controller. Set SCSI Bus Sharing = Physical or Virtual and have fun :)