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"Parallels is a worldwide leader in virtualization
and automation software that optimizes computing for consumers, businesses, and service providers across all major hardware, operating system, and virtualization platforms."
Source : Parallels
Top Ten Considerations For Choosing A Server Virtualization Technology
Server Virtualization Technology is also known as:
Virtual Server Environment,
server consolidation virtualization,
Virtual Disaster Recovery,
Introduction server virtualization,
The playing field for server virtualization has become much more crowded over
the last few years. Competition is always good for a
market as more choices always push vendors into providing better products at
more competitive prices. It can be very time consuming to digest each vendor's
marketing materials to come to the right solution for your organization. This
checklist provides a list of the main considerations and basic differences
between the technologies to provide a starting point for technology evaluation.
The three main technologies discussed in this analysis are: hardware
virtualization, para-virtualization and OS virtualization.
Hardware virtualization is probably the most commonly known technology,
including products from VMware, Parallels and Microsoft. The technologies are
designed to support multiple types of OSs on a single server and are
characterized by technology that virtualizes hardware resources in order to
manage and dedicate them to Virtual Machines on the server.
Para-virtualization is similar to hardware emulation because in concept it is
designed to support multiple OSs on a single server. The only implementation of
this technology today is the Xen open source project. Xen customizes the
operating system to provide more efficient processing and lower overhead which
results in better performance than hardware emulation.
OS virtualization is a third approach to virtualization and has been
implemented by SWsoft's Virtuozzo and Sun's Solaris Containers. The concept is
based on a single OS instance, which provides a leaner more efficient
architecture and a single OS per server for management and updates. The main
limitation is that it does not support multiple OSs on the same server so it is
intended for organizations that are consolidating or deploying multiple virtual
servers on a single Linux, Windows or Sun physical server; Solaris Containers
obviously supports Solaris while Virtuozzo supports both Linux and Windows.
SWsoft Virtuozzo for Linux product does support multiple Linux distributions in
the guest virtual servers.
Many organizations undertake virtualization projects because they can
quantify the hard costs of hardware sitting in data centers at 15-20%
utilization rates. While hardware and environmental costs are considerable, the
administrative costs for managing servers are the largest cost component.
Administrative tasks include OS and application updates and patches, backups,
installations and provisioning.
The management tools available for each solution vary widely. Some solutions
have very few tools available and may be extremely limited. There are many
excellent toolsets available with the more mature products.
The process of moving a physical server to a virtual server can be daunting
task, particularly if the server is critical to the business. Most of the
vendors have tools that help in the migration process, and there are some
external vendors that have provided tools for moving not only from physical to
virtual, but between virtual environments and even from virtual back to
physical. The ability to evaluate a physical server for resource utilization
trends to predict and configure an adequate virtual server is rated as the most
important component for physical to virtual transition, even above the simple
requirement of moving data reliably to a virtualized server. The resource
trending capability is only available in a few select P2V tools.
#2. Virtualization Level
Para-virtual and hardware virtualization solutions virtualize the technology
from the hardware up to the OS. OS virtualization sits on top of the OS,
virtualizing a single instance on a server and taking advantage of all of the
underlying hardware technology. Hardware virtualization looks exactly like a
dedicated server, ten servers consolidated onto one will still have ten plus one
OS virtualization requires only a single OS instance, although in certain
cases OS variances are supported. With the ease of deploying virtualized
servers, hardware virtualization sites have actually seen an increase in the
number of virtualized servers, beyond what would have been approved on a single
server basis. With the complete OS and application structure of each virtualized
server, the management workload for IT teams has gotten even larger, rather than
decreased with these types of virtualization solutions. OS virtualization
deploys on a single OS per server, limiting it to a single OS type, but in the
case of management this is quite beneficial.
Why is processing overhead important? It affects the performance of the
application, and ultimately the end-user's satisfaction. Only non-production or
non-critical applications should be loaded in a virtualization infrastructure
that is high in processing overhead. The processing overhead of virtualization
solutions ranges from 1% to as much as 60% between the different product
offerings; the virtualized application could perform at near native performance
or so slowly it is unacceptable by the end-user. The products in each
virtualization technology category vary largely for performance, but generally,
the hardware virtualization has the most performance degradation, and the OS
virtualization has the closest to native performance.
Many customer virtualization projects are a result of examining server
utilization rates which typically are as low as 5-15%. Raising server
utilization rates can considerably reduce total cost of ownership of data center
resources. Often the new servers that house the consolidated servers are robust
with high processing power and capacity, and a single additional virtualized
server makes a fast impact on the return on investment analysis. Some
virtualization solutions have limitations on the number of virtualized servers
allowed on a single server, and other solutions cannot support many virtualized
servers based on their architecture and high overhead.
OS virtualization technologies are unique in addressing utilization. There
are no limitations on the number of virtualized servers allowed on a single
physical server, and the efficient architecture enables many more virtual
servers to be supported with adequate processing power on a single physical
server which can deliver significantly higher actual "useful" utilization
(utilization that does not include overhead as part of it) and associated
maximum performance/price ratios and ROI.
#5. Platform Support
Virtualization technologies abstract the virtual servers from the underlying
hardware. However, that does not mean that any hardware is supported by the
virtual infrastructure. Hardware virtualization and para virtualization in
particular have to support each piece of hardware, from straightforward CPU
chips to obscure video cards. OS virtualization technologies by definition are
built on top of standard OSs and therefore automatically support all of the
hardware that the OS supports making them easier to deploy with fewer conflicts.
In addition to baseline hardware support, some technologies are able to leverage
full hardware technology capabilities inside of virtual machines including full
SMP support, 6 bit processing, up to 16 CPUs and up to 6 GB of RAM.
One of the largest benefits of virtualizing a server is abstracting it from
the hardware layer and enabling it to move between servers. Migration
capabilities allow cloning or moving a virtualized server from one physical
server to another. The benefits of migration include:
- Eliminating downtime for hardware upgrades or issues
- Avoiding downtime as a result of software changes
- Moving virtualized server to a more or less powerful server as
Many virtualization solutions have cloning or migration capabilities but they
vary considerably in capabilities, restrictions and cost structures. A very
high-end solution that allows zero-downtime migration is extremely costly and
requires a SAN, while another available solution provides near-zero downtime on
any networked server as a part of the basic software package. Assess the
importance of migration and how it will be used to determine the best it for
#7. Resource Management
The three technology categories approach resource allocation in different
ways. Hardware virtualization and para-virtualization virtualize hardware
resources for dissemination to each of the residing virtual servers. The
products have varying levels of flexibility for assigning and changing
resources. Some resources are dynamic and able to change in real-time, while
others require a server reboot or at least virtual server interruption. These
two technologies actually assign a virtualized hardware resource to a virtual
server; virtualized resources can have limitations such as limited CPU and
memory that can be assigned to a single virtual machine
OS virtualization has flexible resource management. Resources may be changed
in real-time without interrupting the application or the virtual server. SWsoft
in particular allows bursting, which allows unclaimed resources on the server to
be used by any virtualized server requiring resources.
#8. Isolation & Security
Each of the technologies has a different approach to isolation and security.
The most basic component of a virtualization solution is partitioning. Each
virtual machine must be completely isolated so that processes, DLLs, and
applications do not affect others on the same server.
The technologies change access points and different components of a regular
server so attacks are less likely to be a problem for virtualized servers. Along
the same lines of isolation, security between the virtual machines on the same
server is also critical. Each of the technologies has a different approaches to
these areas, and with the exception of XEN and Solaris Containers, have been
tested extensively by enough customers to validate effective levels of isolation
#9. Intended Virtualization Deployment
The top three server virtualization deployments are testing and development,
server consolidation, and disaster recovery.
Testing and development organizations were the first to deploy virtualization
technologies because the need for developers to use many different operating
systems made it quite difficult to manage the associated costs. For development
organizations that need different operating systems, one strong option is
hardware virtualization. Para-virtualization has plans to support multiple
operating systems but hasn't launched that capability. SWsoft's Virtuozzo for
Linux does support different Linux distributions on the same server, but does
not mix OS families. For testing organizations that need to be able to quickly
create many servers for stress testing, most of the technologies would be
sufficient although some have much faster provisioning capabilities.
Server consolidation (involving existing applications and/or new
applications) is typically done on servers in production supporting live
applications and data. The two most important considerations for server
consolidation are processing overhead and server utilization. The best
technology suited for server consolidation is OS virtualization because it has
low overhead and servers it enables has therefore significantly higher
Disaster recovery solutions are a very common virtualized server deployment.
Many organizations find that fully available and redundant systems are too
costly for disaster recovery. Virtualized servers that can be activated, booted
and made primary servers in a limited amount of time are rapidly becoming the
cost-effective and more manageable disaster recovery solutions of choice. There
are differences in the technologies regarding boot time and there are other
tools and components that may be purchased to supplement server availability.
#10. Capabilities And Performance Comparison
Finally, the last consideration is comparing the performance and
capabilities. Many of the solutions have trade-offs within the technology and
the comparison chart on the next page highlights those differences.
Server Virtualization Evaluation Worksheet
|#1. Management Tools
|#2. Virtualization Level
|#5. Platform Support
|#7. Resource Management
|#8. Isolation & Security
|#9 Intended Virtualization Deployment
|#10. Capabilities & Performance Trade-off
There are three main server virtualization technologies, each with some
inherent strengths and limitations based upon their architectures. Each
technology is suited best for a particular type of virtualized server scenario.
Within each category, the solutions and tools from each vendor vary
dramatically. Hopefully this checklist will assist in an evaluation of a server
virtualization technology and help find the most appropriate solution for your
For more information about SWsoft and Virtuozzo please visit
www.virtuozzo.com or contact us at
Table of Contents
- Technology Overview
- Ten Considerations
- Management Tools
- Virtualization Level
- Platform Support
- Resource Management
- Isolation & Security
- Intended Virtualization Deployment
- Capabilities and Performance Comparison
- Server Virtualization Evaluation Worksheet