Information Technology Reference
In-Depth Information
Table 1.1 Virtualization Conversions
P
V
P
P2P
Move a system
(Tools predate virtualization)
P2V
Virtualize a system, sometimes as part of
consolidation
V
V2P
Un-virtualize
Uncommon, rarely used
V2V
Migrate a VE to another system, or convert to an-
other VE technology via a standard image format
1.1.6.6 Maintaining a Legacy Operating System on New Hardware
Thousands of older computers are running operating systems that are a version
or more behind the current version. The difficulty of upgrading these computers
to use new hardware or a new version of the OS varies. In some cases, software
tools can be used to upgrade the operating system while the application is still
running. Others systems are simply impossible to upgrade. Many systems fall be-
tween those two extremes.
For many of those systems, the best choice is rehosting the application on new
hardware with new operating system features while still maintaining the applica-
tion and its configuration. Achieving this “best of both worlds” solution requires a
low-level layer of software—for example, a new version of an operating system that
can pretend to be an old version. The new version would provide a virtual instance
of an old version. This can be accomplished with a layer of software that translates
old system calls into new ones. The result is the ability to maintain an older applica-
tion environment while also benefiting from a new OS and new hardware.
1.1.6.7 Flexible, Rapid Provisioning
The computer industry has developed many solutions to address the challenge of
deploying an operating system on a computer. These software solutions rely on
the use of low-level tools embedded in the hardware of the target system. Because
they are simple tools, their flexibility is limited, and the provisioning software
must take on almost all of the burden of OS deployment. For example, hardware
features do not usually include a simple command to install an OS image from a
repository to local disk and boot from it. Also, because provisioning systems rely
on hardware from different manufacturers, many methods must be maintained in
an up-to-date state.
Virtualization can provide a rich set of tools as a foundation on which virtual
environments are deployed. Its use simplifies the software that deploys virtual en-
vironments. An industry standard, VMDK, has been developed for an x86 operat-
ing system image, enabling the deployment of an image created with one vendor's
hypervisor onto that of another vendor simply by copying the image.
 
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