In one aspect, the invention relates to a fault tolerant computing system. The system includes a primary virtual machine and a secondary virtual machine, wherein the primary and secondary virtual machines are in communication, wherein the primary virtual machine comprises a first checkpointing engine and a first network interface, wherein the secondary virtual machine comprises a second network interface, wherein the first checkpointing engine forwards a page of memory of the primary virtual machine to the second virtual machine such that the first checkpointing engine can checkpoint the page of memory without pausing the primary virtual machine.