Patent ID: 8423732

Claim:
A method for accessing a writable virtual disk (vdisk) residing in an active file system on a storage appliance executing a storage operating system, comprising: creating a backing store from an existing vdisk of the storage operating system, wherein the backing store comprises a read-only version of the existing vdisk; creating a new vdisk in the active file system; binding the new vdisk to the backing store to create the writable vdisk, wherein the writable vdisk is a sparse file in the active file system, wherein the sparse file consumes no storage space at creation, wherein the new vdisk is bound to the backing store using an attribute specifying the backing store; receiving a read access request for a block associated with the writable vdisk; determining whether the requested block is stored in the writable vdisk; in response to determining that the requested block is not stored in the writable vdisk, accessing data from a block allocated to the backing store; and in response to the read request, returning the accessed data.