Virtualization

Submitted By: SubmittedTo.
Ms. Prachi Rawal Mr. Hemant Sahu
MCA 5th Sem.(3rdYear) Assoc.Prof.&Head
Of MCA Department

 The journey toward the cloud begins with
virtualization.
 Virtualization has emerged as the key
disruptive technology that has catalyzed and
enabled data centres to deliver cloud
services.
 Compute, networks, and storage form the
three infrastructure pillars of today’s data
centre.
by:Mr.Abhishek Khare

 The idea of virtualization is not new; it has
been around since the days of the mainframe.
 But more recently, the term virtualization
has gained a broader, more inclusive
connotation beyond server virtualization.

 Virtualization can be defined as the abstraction of
physical resources into logical units, such that a single
physical resource can appear as many logical units
and multiple physical resources can appear as a single
logical unit.
 The primary motivation behind virtualization is to
hide the physical characteristics and irrelevant details
of these resources from their end users.
 Thus, each user gets the illusion of being the lone user
of that physical resource (one-to-many virtualization).
Or multiple physical resources appear as a single
virtual resource to the user (many-to-one
virtualization).

 Consider the familiar example of virtualizing
an x86 server, where software, called virtual
machine monitor (VMM) or hypervisor ,
allows multiple virtual machines (VM) to run
on the same physical server, as illustrated in
Figure

 Each VM emulates a physical computer by
creating a separate operating system
environment.
 The ability to run multiple VMs means that we
can now simultaneously host multiple operating
systems on the same underlying physical
machine. Each operating system gets the
illusion that it is the only one running on that
host server.
 One physical machine has effectively been
divided into many logical ones.

 Virtual LANs (VLAN) are another example of
one-to-many virtualization, where a single
physical network is partitioned into many
logical ones.
 Instead of setting up separate physical
networks for each user group, a single
physical network infrastructure can suffice,
with each user group assigned to a separate
logical network (VLAN).

 The classic example for many-to-one
virtualization is that of a load balancer, which
front ends a group of web servers. As shown
is Figure

 The load balancer hides the details about the
multiple physical web servers and simply
exposes a single virtual IP (VIP).
 The web clients that connect to the VIP to
obtain the web service have the illusion that
there is a single web server.
 Many physical web servers have been
abstracted into one logical web server.

 The concept of virtualization has been around
since the 1960s, when IBM implemented it to
logically partition mainframe computers into
separateVMs.
 This partitioning enabled mainframes to run
multiple applications and processes at the
same time, which improved their utilization.
 Such multitasking allowed better leveraging
of those expensive investments.

 Over the next two to three decades, the need for
virtualization declined as inexpensive PCs and servers
became available.
 In addition, client/server applications became
prevalent, and the trend shifted toward distributed
computing. Furthermore, the universal adoption of
Windows and Linux led to the emergence of x86
servers as the dominant compute platforms.
 Unlike mainframes, however, these servers have not
been designed for virtualization. To enable the
virtualization of x86 servers, specialized software
called hypervisor was developed by companies such
asVMware, Citrix, Microsoft, and others.

 The term virtualization has evolved beyond server
virtualization into a significantly broader context.
 Today, it represents any type of process obfuscation
where a process is removed from its physical
operating environment.
 Therefore, virtualization can be applied to other areas
of IT, such as storage, network, applications, services,
desktops, and many more.
 This chapter focuses on server virtualization, network
virtualization, and storage virtualization, which
together form the foundation of today’s virtualized
data center.

 Server or compute virtualization is the most
popular and visible form of virtualization today.
 We briefly touched on this form of virtualization
as an example of one-to-many virtualization and
saw how low-level software (hypervisor or VMM)
allows multiple operating systems to run
concurrently on a single host computer.
 As Figure 1-1 illustrated, each operating system,
along with its applications, runs in complete
isolation as a VM on top of the hypervisor, under
the illusion that it is the sole operating system
running on that physical machine.

 To successfully virtualize the system and
enable multiple VMs to run concurrently on
the same host, hypervisors dynamically
partition and share the available physical
resources, such as CPU, memory, and I/O
devices. The functionality of the hypervisor
varies greatly based on the architecture and
implementation.

 CPU, memory, and I/O are typically
considered the three vital resources of a
server.
 Correspondingly, the three key components
of server virtualization are CPU virtualization,
memory virtualization, and I/O virtualization .
The sections that follow take a look at all
three components, starting with the
virtualization of the x86 CPU.

 Beyond CPU virtualization, the other critical
part of server virtualization is memory
virtualization. This involves sharing the host
physical memory (machine memory) and
dynamically allocating it to VMs, as illustrated
in Figure 1-4 .
 VM memory virtualization is similar to the
virtual memory support provided by modern
OS.

 Applications see a contiguous address space
that is not necessarily tied to the underlying
physical memory in the system.
 The operating system keeps mappings of
virtual page numbers to physical page
numbers stored in page tables.
 All modern x86 CPUs include a memory
management unit (MMU) and a translation
look-aside buffer (TLB) to optimize virtual
memory performance.

 Having coveredVMs (CPUs) and then virtual
memory, this discussion now turns to the final
component of the server virtualization story: I/O
virtualization (IOV).
 As the name suggests, IOV involves virtualizing
the I/O path from the server to the peripheral
device, enabling multipleVMs to share an I/O
device.
 As shown earlier in the case of CPU and memory
virtualization, even in IOV we have a software
approach and a hardware approach.

 A virtual storage area network (VSAN) is a
logical partition in a storage area network
(SAN). VSANs allow traffic to be isolated
within specific portions of a storage area
network.

 The use of multiple VSANs can make a system
easier to configure and scale out. Subscribers
can be added or relocated without the need for
changing the physical layout.
 If a problem occurs in one VSAN, that problem
can be handled with a minimum of disruption to
the rest of the network.
 Because the independence of VSANs minimizes
the total system's vulnerability, security is
improved. VSANs also offer the possibility of
data redundancy, minimizing the risk of
catastrophic data loss.

 The term is most often associated with Cisco
Systems and is often mentioned in
conjunction with the zoning. Zoning splits a
SAN into multiple, isolated subnetworks.
 The concept behind a VSAN is often
compared to that of a virtual local area
network (VLAN).
 VLANs segregate broadcasts from other
networks

 In computer networking, a single layer-2
network may be partitioned to create
multiple distinct broadcast domains, which
are mutually isolated so that packets can only
pass between them via one or more routers;
such a domain is referred to as a virtual local
area network, virtual LAN or VLAN.

Virtualization

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