A computer system, having: a physical computer, which includes a processor and a memory; and an external apparatus, which is coupled to the physical computer and which includes a storage apparatus, the physical computer further includes: a virtualization module for providing at least one virtual machine; a first failure monitoring module for detecting a failure in the physical computer and the virtualization module; a first memory dump module for copying, to the external apparatus, a first area in the memory which is allocated to the virtualization module; a second failure monitoring module for detecting a failure in the virtual machine; and a second memory dump module for copying, to the external apparatus, a second area in the memory which is allocated by the virtualization module to the virtual machine.