Oracle releases paravirtualized drivers for Windows guest OSes – UPDATED

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Yes, Oracle is slowly increasing the frequency of its incursions in the virtualization world.
Now that the company controls three hypervisors (its own Oracle VM, Sun xVM Server and Virtual Iron) it’s expected that a master plan comes out sooner or later.

For now Oracle just shows a little piece of it, by announcing its paravirtualized (PV) drivers for Windows guest OSes.

Oracle offers them for Windows Server 2003 and 2008 as well as for Windows XP and Vista. For each one there’s a 32bit and a 64bit version. Of course they are only available for the Oracle VM hypervisor.

The paravirtualized drivers improves the performance of virtual machines when there’s no chance to leverage the capabilities of hardware-assisted virtualization technologies like AMD-V RVI (available in the Quad-Core Opteron CPUs since September 2007) and Intel EPT (available in the new Xeon 5500 CPUs).

While enhancing the performance of Windows guest OSes, the PV drivers that Oracle is shipping also imply some limitations: once installed them, the virtual machines state can’t be saved and restore anymore and live migration is no more available.

It’s interesting to note how different is the current Oracle approach compared to the one of its new subsidiary Virtual Iron.
Exactly three years ago Virtual Iron
announced its intention to stop the development of PV drivers:

…Paravirtualization requires substantial engineering efforts in modifying and maintaining an operating system. However, these heroic efforts are inevitably losing the battle against Moore’s Law and hardware advances being made in the x86 space. By the time the first product with paravirtualization appears on the market, more than 80% of the shipping x86 server processors from Intel and AMD will have hardware-based virtualization acceleration integrated into the chips (Intel-VT and AMD-V or “Rev-F”). This hardware-based acceleration is designed to optimize pure virtualization performance, primarily the virtualization of CPU, and it renders OS paravirtualization efforts as completely unnecessary and behind the technology curve…

Update: As some comments below highlighted, the last point in this article, about the divergence of opinions between Oracle and Virtual Iron on paravirtualization is wrong.

In 2006 Virtual Iron was rejecting the idea of running fully paravirtualized guest OSes (which requires kernel patching). 
Oracle is not taking a different approach. It’s just releasing paravirtualized drivers to speed the I/O operations, something that all the other virtualization vendors do as well through guest OS packages that customers are recommended to install (like the VMware Tools).