Using process checkpointing is indeed one good way to implement fault tolerance. The Irmin style is more explicit -- the heap itself is tree structured, and the application uses it to checkpoint itself to disk/memory as a matter of course.

This ensures that only the minimal state required is stored (as opposed to the entire process heap), and also that state can be reconstructed intelligently to preserve sharing and special resources. For instance, file descriptors (if running in Unix mode) could be reified to a filename/offset and reopened, and memory mapped areas (such as the shared ring structures that Xen uses) could be re-granted from the hypervisor.