Feeds

Virtualisation for Beginners

It's not just for server jockeys, you know

  • alert
  • submit to reddit

High performance access to file storage

This is something that Windows itself has always purported to be able to do since the arrival of XP, but - in my experience at least - the success rate has been less than sterling. A VM snapshot, by contrast, is equivalent to a complete new installation on brand new hardware with a slipstream update of all your apps up to the last point of failure.

Virtualisation for Beginners

Technically, if perhaps not legally, you can run Mac OS X in a VMWare virtual machine under Windows

The Technology Behind the Magic

Virtualisation originated in IBM's big mainframes of the 1960s and 1970s when the company hit on the idea of installing a thin software layer, the 'hypervisor' immediately above the hardware that would allow multiple operating systems to run simultaneously side by side without impacting on one another or even necessarily being aware of each others presence.

'Simultaneously' needs some qualification here, because the various operating systems in fact time-shared a single CPU. But the switching would take place fast enough - several thousand times a second - to create the illusion of simultaneity.

Multi-tasking operating systems use a similar technique to run multiple apps at the same time. In this scenario, called 'context switching', only the metrics associated with each running app - the 'state' of the app - need be stored. When switching between complete guest operating systems much more data has to be saved between each switch: the total state of the guest operating system itself, as well as the states of all the apps it happens to be running at the time. Engineers call this a 'world switch'.

A Solid Proposition

The earlier Pentium processors weren't designed with virtualisation in mind. But using a software technique called 'segment faulting', developers managed to introduce world switching, and hence virtualisation to Pentium-class processors in the late 1990s. The first VMware product allowed Windows to run in a virtual machine on a Linux host, and this technology was later extended to use Windows as a host for Linux and other operating systems.

Virtualisation for Beginners

Parallels 5 for the Mac allows you to set an 'Active Corner' when in Full Screen mode

By 2006, even modest desktop processors from Intel and AMD were becoming powerful enough for virtualisation to be a solid proposition. And that, literally, is what it became. The two x86 companies each introduced hardware assistance for virtualisation into its processors: AMD-v - codenamed 'Pacifica' - and Intel's own VTx - 'Vanderpool' - were similar but different hardware virtualisation support systems.

Combat fraud and increase customer satisfaction

More from The Register

next story
This time it's 'Personal': new Office 365 sub covers just two devices
Redmond also brings Office into Google's back yard
Oh no, Joe: WinPhone users already griping over 8.1 mega-update
Hang on. Which bit of Developer Preview don't you understand?
Microsoft lobs pre-release Windows Phone 8.1 at devs who dare
App makers can load it before anyone else, but if they do they're stuck with it
Half of Twitter's 'active users' are SILENT STALKERS
Nearly 50% have NEVER tweeted a word
Internet-of-stuff startup dumps NoSQL for ... SQL?
NoSQL taste great at first but lacks proper nutrients, says startup cloud whiz
Ditch the sync, paddle in the Streem: Upstart offers syncless sharing
Upload, delete and carry on sharing afterwards?
New Facebook phone app allows you to stalk your mates
Nearby Friends feature goes live in a few weeks
Microsoft TIER SMEAR changes app prices whether devs ask or not
Some go up, some go down, Redmond goes silent
Batten down the hatches, Ubuntu 14.04 LTS due in TWO DAYS
Admins dab straining server brows in advance of Trusty Tahr's long-term support landing
prev story

Whitepapers

SANS - Survey on application security programs
In this whitepaper learn about the state of application security programs and practices of 488 surveyed respondents, and discover how mature and effective these programs are.
Combat fraud and increase customer satisfaction
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Top three mobile application threats
Learn about three of the top mobile application security threats facing businesses today and recommendations on how to mitigate the risk.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.