1. A computing system comprising: a plurality of virtual machines, including a first virtual machine, and a hypervisor executing on a first host; a storage system comprised of a plurality of physical storage devices that are accessed by the plurality of virtual machines, wherein the plurality of physical storage devices are organized into a storage pool, which is a layer of abstraction for managing the physical storage devices, wherein logical units of storage for storing virtual disks for the plurality of virtual machines, including a first virtual disk for the first virtual machine, are allocated from the storage pool; and a virtualized disk I/O handler executing on the first host and configured to handle disk access requests from the virtual machines that are intercepted by the hypervisor, by generating access requests to the logical storage units, and receiving and forwarding responses from the logical storage units to the requesting virtual machines, wherein a disk access request for the first virtual disk from the first virtual machine is intercepted by the hypervisor and handled by the virtualized disk I/O handler, wherein the virtualized disk I/O handler is configured to modify each of the disk access requests for the first virtual disk, which includes a unique identifier for the first virtual disk and a location within the first virtual disk to be accessed, with identifying information for one of the logical units of storage storing the first virtual disk and a location to be accessed within said one of the logical units; and, wherein the virtualized disk I/O handler is configured to allow or not allow each disk access request to proceed based on the location to be accessed in said one of the logical units.