Page 190 - Cloud computing: From paradigm to operation

1 Framework and requirements for cloud computing

Interconnect network

Processing unit 1 Processing unit 2

Management component
CPU Memory Storage I/O
CPU Memory Storage I/O CPU Memory Storage I/O …

Motherboard Motherboard

Power supply Cooling
Power supply Cooling

Enclosure

Figure 6-5 – Example of a multi-processing unit type

6.4 Virtualization in physical machines

This clause identifies different types of virtualization of the components in processing units such as CPUs,
memory and I/Os. The mode of virtualization in each component can be software based mode or hardware-
assisted mode. The requirements in this Recommendation only consider the hardware-assisted mode for
virtualization.
6.4.1 CPU virtualization

CPU virtualization technology makes a single CPU act as if it was multiple individual CPUs. There are different
ways to implement CPU virtualization. CPU virtualization can be implemented in software-based mode and
in hardware-assisted mode:
– In software based mode, the privileged instructions are simulated by software.

– In hardware-assisted mode, the privileged instructions can be directly run by the physical CPU to
achieve higher performance. Hardware-assisted mode requires the CPU to support a virtualization
instruction set.
NOTE – The difference between the two modes is in the execution of privileged instructions in VM's operating system
(OS).

6.4.2 Memory virtualization

Memory virtualization abstracts physical memory to a divided virtual memory for use by a virtual machine.
There are two modes of memory virtualization: software-based and hardware-assisted memory
virtualization:
– Software-based mode builds a software based memory mapping table.
– In hardware-assisted mode, a memory mapping table is implemented in hardware with better
performance.
NOTE – The difference between the two modes is the mapping between virtual memory and physical memory.

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