XenPR also uses a small kernel image that takes control
when a crash occurs. However, XenPR relies on saving the
process state using files, which are used later to restore
the processes to their pre-crash states. This is similar to
the checkpoint/restart technique. XenPR currently does not
handle a large number of process types (e.g., processes with
open sockets and processes that use IPC mechanisms). The
approach also incurs overhead because of the need to start
the small kernel and save the state into files. In contrast,
ALDR does not need to do any state saving into files, as
ALDR directly accesses in memory the state of the entire
crashed-OS instance with the help of the hypervisor. Also,
because ALDR resurrection does not require a full LPAR
(Logical PARtition) initialization and OS re-IPL (Initial
Program Load), the whole process is very fast.