Virtualization

Supplemental Material beyond the textbook

What is Virtualization?

• The term virtualization is used very broadly in the

computing industry can refer to:

• Hardware, software, storage, data, networks, etc.

• E.g. a hard drive partitioned into multiple virtual

drives, a virtual LAN or a virtual private network

• Virtualization in our context is more specifically

known as Platform Virtualization, the idea that

the hardware platform will be virtualized to

support many operating systems

What is Platform Virtualization?

• Platform Virtualization is often referred to as

Server Virtualization because servers were

the first target to virtualize (largely for money

savings)

• Platform Virtualization also includes Desktop

Virtualization, which is increasingly used as

companies look for ways to cut their PC

procurement and operating budgets

What is Virtualization?

• Virtualization is the idea that one computer can run multiple operating systems concurrently

• This idea is not new – mainframes have been providing virtualization capabilities for over 40 years

• Increases in computing power in Intel architecture computers is making virtualization very important

Hypervisor

• A hypervisor, also called virtual machine monitor (VMM), is a computer software/hardware platform virtualization software that allows multiple operating systems to run on a host computer concurrently.

• The base computer is known as the “host”, and the operating systems running on the host are known as “guests”

Types of Virtualization

• Type 1:

• Also referred to as native or bare-metal.

• Software systems that run directly on the host's

hardware as a hardware control and guest

operating system monitor

• Type 2:

• Software applications running within a

conventional operating system environment

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Type 1 Virtualization Type 2 Virtualization

Why Virtualize?

• Modern hardware has enormous processing capabilities

(current Intel Xeon chips have 8 CPU cores supporting 2

threads per core; a server may have 4 of these)

• Consolidating servers saves electricity, cooling costs, and

rack space in the server room

• Saving electricity means a lower carbon footprint, important

to companies as they assess their environmental impact

• Run different OS’s simultaneously on one computer

• Disaster Recovery planning can be simplified by using

virtualized operating systems

Example: Consolidation

• You have 20 existing SERVER computers

– Each with two 3GHz CPUs

– Each with 4 GB RAM

– Each need about 500 GB disk space

• Propose a replacement plan using virtualization

– Replace with servers that have 16 2 GHz CPU cores

– How many physical computers?

– How much RAM?

– How much disk space?

Example: Consolidation

Total processing power of the existing servers is

20 * 2 * 3GHz = 120 GHz

– Total RAM of existing servers is 20 * 4 = 80 GB RAM

– Total Disk of existing servers is 20 * 500 GB = 10 TB

If a new server has 16 * 2 GHz = 32 GHz processing, we

need about 4 new servers with 20GB RAM each and 2.5

TB disk each to replace the existing servers

– Important – if you were really doing this, make sure you purchase

one spare server!

Example: Electrical Savings• Original 20 computers consume 250 Watts, new computers

EnergyStar rated and consume 240 Watts

• Total annual energy consumption in KW hours =

# servers * Watts consumed * 365 days * 24 hours / 1000

• Total annual energy cost = Total annual KW hours * KW

hour cost (the average US cost of a KW hour is ten cents)

• Original 20 computers: – Annual KW hours = 20 * 250 * 365 * 24 / 1000 = 43,800 KWh

– Annual energy cost = 43,800 * $0.10 = $4,380

• New 4 computers: – Annual KW hours = 4 * 240 * 365 * 24 / 1000 = 8,410 KWh

– Annual energy cost = 8410 * $0.10 = $841

Disaster Recovery

• Servers fail due to

• Software: after installing patches or new software applications

• Hardware: a piece of hardware fails and the machine stops

• In a traditional computer, these failures may require

reloading the operating system and applications, or

rebuilding the hardware

• In a virtualized environment, the entire guest OS server

exists as a file. This means if a server fails due to

• Software: you can simply replace the file with a recent copy from

backup and restart the guest OS

• Hardware: you can move the file to another computer and start the

guest OS

Estimating Effects of Virtualization1. Estimate resources being replaced as:

• Processing Capacity per PC (CPUpc) * No. of PCs (#PC) = Required CPU processing speed (CPUr)

• RAM per PC * No. of PCs = required RAM (RAMr), and Disk storage per PC * No. of PCs = Disk Storage (HDr) required

• Adjust as needed – room for growth? Idle resources?

2. Estimate No. of server machines (SMr) needed as:

• CPUr / CPU Capacity per server machine (CPUsm)

3. Estimate RAM required per server machine as:

• RAMr / SMr

4. Estimate Hard Disk required per server machine as:

• HDr / SMr

5. Add server machine(s) (SMft) needed for fault-tolerance to get final count of server machines required -> SMrf = SMr + SMft

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