1. A method comprising: receiving a request in a first computer system for an image of a virtual machine during execution of the virtual machine on the first computer system, wherein the virtual machine comprises at least one application, an operating system on which the application is designed to execute, memory data to which the application and operating system have access, and one or more virtual disks including one or more files accessed by the application or operating system; creating an image of the virtual machine in response to the request and without suspending the virtual machine, wherein the image comprises at least the one or more files on the one or more virtual disks and the memory data; and tracking which memory locations within a memory of the virtual machine are modified by the application or operating system during the creation of the image, wherein the modifications are tracked separate from the memory data included in the image.