1. A part of the operating system is "resident" if it is always in memory, and "virtual" if it can be stored instead in virtual memory on disk. Which parts of an operating system must be resident, and which can be virtual? Why? 2. The linux disk journal is an apparent contradiction of the basic principle that the disk driver manages all device state. What states of the disk are controlled by the actual driver, and which are controlled by the journalling subsystem in an application program? Why?