Virtualization: All About Hypervisors
Virtualization is arguably the technology trend of year. As virtualization — or at least talk of it — spreads through the enterprise, the word hypervisor is popping up everywhere in
conjunction with it. To understand what a
hypervisor is, you first have to have a basic understanding of system
virtualization.
What is Virtualization?
In plain and basic words,
virtualization is used to improve IT throughput and costs by using
physical resources as a pool from which
virtual resources can be
allocated. If that is still a bit too much to swallow, consider then,
the simple scenario of
partitioning a computer
hard drive. A single
physical hard drive is partitioned and it effectively creates two
separate hard drives in terms of how it is seen. While you still
have only a single physical hard drive in your system, this act of
virtualization allows the computer system, devices and human
users to work with that single hard drive as if it were two physical
hard drives.
Virtualization, of course, goes far beyond the simple act of
partitioning a hard drive however. This year
storage virtualization has
been a hot topic. Storage virtualization is the amalgamation of multiple
network storage devices into what appears to be a single storage unit,
which is somewhat of the opposite effect of partitioning a hard drive.
There is also
server virtualization, which is the partitioning a
physical server into smaller virtual servers.
Network virtualization
uses network resources through a logical segmentation of a single
physical network. And the list goes on to cover
operating system
virtualization and even
application virtualization.
System Virtualization: Hardware &
Hypervisors
System virtualization is a technology often used to consolidate systems,
workloads and
operating environments by using a single physical system
to create multiple virtual systems. One type of system virtualization is
done through hardware partitioning, which divides a single physical
server into partitions — where each partition is able to run an
operating system.
Hypervisors (also called Virtual
Machine Monitor (VMM) or virtualization manager), is another technology at heart of
system virtualization. A
hypervisor provides the underpinnings for virtualization management,
which includes policy-based automation, virtual hard disk, life cycle
management, live migration and real-time resource allocation. It's the
software program or part of the code in
firmware that manages either
multiple operating systems or multiple instances of the same operating
system on a single computer system. The hypervisor's job is to manage
the system's processor, memory and other resources to allocate what
each operating system requires. Hypervisors provide the means to
logically divide a single, physical server or blade, allowing multiple
operating systems to run securely on the same
CPU and increase the CPU
utilization.
Where hardware partitioning allows for
hardware consolidation, hypervisors allow for flexibility in how the
virtual resources are defined and managed, making it a more-often used
system consolidation solution.
Types of Hypervisors
IBM systems breaks hypervisors down
into two different types. Type 1 hypervisors are those that run
directly on the system hardware and offers a higher level of
virtualization efficiency and security.
Type 2 hypervisors are those that run on
a host operating system that provides virtualization services, such as
I/O device support and memory management. Type 2 hypervisors are used
mainly on client systems where efficiency is less critical, and are also
commonly used for systems where support for a broad range of I/O devices
is needed and can be provided by the host operating system.
|
Figure shows one physical system with a type 1 hypervisor
running directly on the system hardware, and three virtual
systems using virtual resources provided by the hypervisor.
[Image Source:
IBM Systems Virtualization Paper (PDF)] |
Figure shows one physical system with a type 2 hypervisor
running on a host operating system and three virtual systems
using the virtual resources provided by the hypervisor.
[Image Source:
IBM Systems Virtualization Paper (PDF)] |
For more information on types of
hypervisors, we recommend reading this IBM Whitepaper resource,
"IBM
Systems Virtualization".
Current Players in
the Hypervisor Market
VMware
VMware's virtual machine (VM) approach creates a uniform hardware
image — implemented in software— on which operating systems and
applications run. On top of this platform, VMware's VirtualCenter
provides management and provisioning of virtual machines, continuous
workload consolidation across physical servers and VMotion
technology for virtual machine mobility. VMware offers a wide range
of products for data center infrastructure, workstations, enterprise
desktops, virtualization accelerators, as well as several free
virtualization products.
Xen
Xen is a virtual machine monitor (VMM) for x86-compatible computers.
Xen is built to securely execute multiple virtual machines, each running its
own operating system, on a single physical system with close-to-native
performance. Xen is open source, and is released under terms of the
GNU General Public License. Xen is a Type 1 hypervisor that runs
directly on the system hardware. Xen originated as a research
project at the University of Cambridge.
Microsoft Virtual
Server
Windows Server virtualization, as a part of Microsoft's
"Longhorn" server, takes a big step forward in bringing some of the advanced
capabilities of virtualization to bear and providing customers with
a scalable, secure and highly available virtualization platform.
Microsoft Virtual Server 2005 R2 is cost-effective server
virtualization technology engineered for the Windows Server System
platform
Intel & AMD Offer
Virtualization
Industry heavyweights like Intel and AMD have also given
virtualization a huge credibility boost. For example, the two chip
vendors are building virtualization capabilities into their chip
architectures — Intel with its
Intel Virtualization Technology (VT)
and AMD with its
AMD-Virtualization (AMD-V), on Xeon and Opteron
processors, respectively. From an application standpoint, the
hardware will enable applications that have previously been hard to virtualize (e.g., I/O-intensive apps like database applications for
which the overhead has been too high) to be virtualized much more
successfully. As Intel's and AMD's technologies are introduced, it
will offer a choice of which virtualization path to explore Windows Server that
of VMware, the market leader; open source software from XenSource;
or an integrated Microsoft solution.
For more information on Intel
Virtualization Technology (VT) and AMD-Virtualization (AMD-V) we
recommend reading this ServerWatch Tutorial: 'Server
Virtualization Goes Prime Time'.
Vangie 'Aurora' Beal -
Writer, www.Webopedia.com
Last updated: November 03, 2006
ServerWatch: Server Virtualization Goes Prime Time
Virtualization technology is enjoying a period of explosive growth at
the moment, and increasing numbers of enterprises are becoming
virtualization converts. Research firm IDC estimates about 750,000
virtual servers were in operation in 2004, and it expects this to rise
to more than 5 million by 2009 . a compound annual growth rate of almost
50 percent.
ServerWatch: Virtually Speaking: The Not-So-Humble Hypervisor
The pervasiveness of virtualization will not be limited to servers.
Gartner analyst Brian Gammage noted in a statement, "Virtualization
support is now being embedded into PCs. By the end of 2007, most of the
PCs sold will come with this capability. The launch of hardware
virtualization support marked the start of a period that will inevitably
lead to the establishment of a critical new PC standard: the
hypervisor."
VMWare
Virtualization Overview WhitePaper (PDF)
Today, virtualization can apply to a range of system layers, including
hardware-level virtualization, operating system level virtualization,
and high-level language virtual machines. Hardware-level virtualization
was pioneered on IBM mainframes in the 1970s, and then more recently
Unix/RISC system vendors began with hardware-based partitioning
capabilities before moving on to software-based partitioning.
Windows Server Virtualization . An Overview (Word Document)
Microsoft is delivering application development tools, server
applications, operating systems, and management solutions that provide
immediate improvements to address the complexity in customers. IT
environment. As a part of the virtualization solutions, customers will
see improvements in the current product offering for Virtual Server 2005
R2; new advanced products such as System Center Virtual Machine Manager
that will address key management challenges and Windows Server
virtualization as a part of Windows Server .Longhorn., that will provide
an improved virtualization platform with increased scalability,
performance and reliability.
Wikipedia: Comparison of virtual machines
The table below compares basic information about virtual machine
packages, including: creator, guest systems supported, license, etc.
Note that these are all Virtual Machines in the 'hypervisor' or
'hardware emulator' sense.
The Xen Wiki
A growing compendium of knowledge about all things Xen. |
