CS533 Concepts of Operating Systems Class 14 Virtualization

CS533 - Concepts of Operating Systems 2 Questions  Is Disco a micro-kernel?  Is it a minimal kernel running in privileged mode?  Does it run OS code at user level?  Does it support modularization of OS code?  What granularity are the modules?  How does it implement protection?  Is virtualization a sandboxing technique?  How does it implement inter-module communication?  Does it support extensibility?  What abstractions does it export to its clients? o What system call interface does it export?

CS533 - Concepts of Operating Systems 3 Questions  At what granularity do VM monitors support multitasking? o How does this differ from conventional multitasking? o How do virtualized CPUs differ from threads/processes? o How do virtualized CPUs differ from scheduler activations?

CS533 - Concepts of Operating Systems 4 Questions  Do micro-kernels do virtualization?  Is a micro-kernel’s use of trap redirection for application binary compatibility the same as a virtual machine approach?  What else is needed for complete virtualization of a machine, such that an OS binary can run on it?

Questions  What characteristics would make a hardware architecture “difficult” to virtualize?  What characteristics would make a hardware architecture “expensive” to virtualize?  What hardware support would be useful for virtualization?  Does virtualization hide any critical characteristics of the real hardware?

Questions  How does virtualization help scalability? o Aren’t we just adding a level of indirection to the same hardware/software base that would not scale?  Why not just use a network of small cheap machines? o What is the advantage of pretending a large shared memory machine is a network of independent machines?