A type 1 hypervisor runs
Answer: A
It is also called a bare metal hypervisor and it is what cloud providers use. A type 2 hypervisor runs as a program on an ordinary operating system and suits development rather than production. Bare metal is the term for the first kind.
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Match each virtualisation term with what it means.
List I
A. Type 1 hypervisor
B. Type 2 hypervisor
C. Guest
D. Host
List II
1. the operating system running inside a virtual machine
2. runs directly on the hardware
3. the physical machine and its hypervisor
4. runs as an application on a host operating system
Answer: B
Correct answer: A-2, B-4, C-1, D-3
The two hypervisor types differ in what lies beneath them: a type 1, or bare metal, hypervisor runs directly on the hardware, while a type 2 runs as an application on top of a conventional operating system. The guest is the operating system inside a virtual machine, and the host is the physical machine together with its hypervisor.
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Assertion (A): Cloud providers use type 1 hypervisors rather than type 2.
Reason (R): Removing the host operating system removes a layer of overhead and of attack surface.
Answer: C
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives both motives. A host operating system beneath the hypervisor adds scheduling and I/O layers that cost performance, and it adds a large body of code whose vulnerabilities would sit under every tenant’s virtual machine. Removing it leaves a thin, purpose-built layer - which is why every major provider runs type 1 and type 2 hypervisors are found on desktops.
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Full virtualisation differs from paravirtualisation in that
Answer: D
Correct answer: the guest is unmodified and unaware
Full virtualisation presents a complete virtual machine, so a stock operating system runs on it without knowing it is virtualised - sensitive instructions are trapped and emulated. Paravirtualisation instead modifies the guest to call the hypervisor deliberately, which performs better but requires a guest that has been ported. Hardware extensions have narrowed the performance gap enough that full virtualisation now dominates.
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Assertion (A): Paravirtualisation has become less important than it once was.
Reason (R): Hardware virtualisation extensions have removed most of the performance penalty of full virtualisation.
Answer: A
Both are true and the reason gives the cause, and paravirtualised drivers for storage and network remain common even where the processor no longer needs help. Hardware support changed the balance. The old advantage has largely gone.
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Consider the following statements about hardware virtualisation extensions.
1. They allow the hypervisor to trap sensitive instructions efficiently.
2. They reduced the need to modify guest operating systems.
3. They eliminate virtualisation overhead entirely.
Answer: B
Correct answer: 1 and 2 only
Statements 1 and 2 are correct: Intel VT-x and AMD-V let the processor trap sensitive instructions directly, which removed both the need for binary translation and much of the case for modifying guests. Statement 3 claims too much - the overhead is greatly reduced but never zero, and it remains appreciable for input and output, which is the subject of two later items here.
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Memory overcommitment allows a host to
Answer: C
Correct answer: allocate more memory than it physically has
Overcommitment works because guests are typically allocated more memory than they use, and the hypervisor reclaims the difference through ballooning, page sharing and compression. It raises the density achievable on a host, which is a direct commercial gain - and it depends on an assumption about behaviour rather than on any physical guarantee.
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Assertion (A): Memory overcommitment must be applied with care.
Reason (R): If guests actually demand their full allocation the host must swap, and performance collapses.
Answer: D
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason is the failure mode. Overcommitment is a bet that guests will not all claim their allocations at once. If they do, the hypervisor must swap guest memory to disk, and since the guest is itself managing memory it has no idea its pages have gone to disk - the result is thrashing, and performance falls by orders of magnitude rather than degrading gracefully.
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Match each memory reclamation technique with what it does.
List I
A. Ballooning
B. Page sharing
C. Compression
D. Host swapping
List II
1. less used pages are compressed rather than swapped
2. a driver in the guest returns pages to the host
3. the last resort, with severe performance cost
4. identical pages across guests are stored once
Answer: A
The techniques are applied in that order of preference as pressure rises. Reaching host swapping means the overcommitment has gone too far. Each technique is tried before the next. Preference runs from cheapest to worst.
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State whether the following is true or false.
Host swapping is the preferred way to handle memory pressure on a hypervisor.
Answer: B
It is the last resort, since the host has no knowledge of which guest pages matter. Ballooning lets the guest itself choose what to release, which is far better. The host cannot see inside the guest. Only the guest knows what it needs.
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