1 : A method to create virtual machines, comprising: creating an initially empty primary copy-on-write image of a base disk image, the base disk image being a template for the virtual machines; creating an initially empty secondary copy-on-write image of the primary copy-on-write image; booting a virtual machine from the secondary copy-on-write image; storing writes by the virtual machine writes in the secondary copy-on-write image; and when the secondary copy-on-write image reaches a capacity threshold, committing data from the secondary copy-on-write image into the primary copy-on-write image and clearing the secondary copy-on-write image.