Wired over server virtualization

HP, IBM, Sun and VMware are charging up their server lines with virtualization. Understanding how each approach would work in your new data center is no easy task.

Virtualization defined: VMware approaches virtualization quite differently from the traditional systems vendors. Rather than building partitioning into the operating system - as HP and IBM have done with HP-UX and AIX - VMware inserts a virtual hardware layer between the operating system and the actual hardware, which serves as an intermediary between the operating system and the physical hardware. This ultimately makes the resulting "virtual machines" portable because the operating system depends on the virtual hardware layer, not the physical hardware.

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VMware

Virtualization defined: VMware approaches virtualization quite differently from the traditional systems vendors. Rather than building partitioning into the operating system - as HP and IBM have done with HP-UX and AIX - VMware inserts a virtual hardware layer between the operating system and the actual hardware, which serves as an intermediary between the operating system and the physical hardware. This ultimately makes the resulting "virtual machines" portable because the operating system depends on the virtual hardware layer, not the physical hardware.

"There's no dependency between the [operating system] and the underlying hardware, so you can take a virtual machine from one system - like IBM running on a RAID array - to a Dell running on a [storage-area network]. The [operating system] is taking the virtual hardware with it," says Michael Mullany, vice president of marketing at VMware.

Anything that runs on x86-based systems can run VMware, including all versions of Windows, Linux and NetWare.

Now that EMC owns VMware, the company is stretching beyond server virtualization to the Virtual Infrastructure, which includes storage and networking.

ESX Server

VMware's ESX Server can be implemented directly on any x86-based platform, running a maximum of a two-processor environment. Mullany says it will support larger environments in the future; last June, it ran only a single-processor environment.

Users can manage pools of ESX Servers via VirtualCenter, VMware's virtual infrastructure management software, which lets administrators shift around resources to minimize unused capacity and quickly provision servers.

Many VMware users administer ESX Server for disaster recovery, testing/development and data center consolidation. In a testing environment, for instance, you can capture the operating system and accompanying application software in a file and copy it to another system, "eliminating four to six hours of rebuilding servers for a new test case," Mullany says.

Because VMware is the only way of creating virtual partitions on x86-based servers - outside of Microsoft's own Virtual Server and eventual Longhorn operating system - the company has developed close relationships with many server vendors, including Dell, HP, IBM and NEC.

Distributed virtualization

As part of its VirtualCenter, VMware also has developed a "distributed virtualization" system - called VMotion - that migrates a running virtual machine to a different physical server without service interruption. "What this allows you to do is almost immediately rebalance how workloads are consuming system resources across a pool of hardware," Mullany says. "If you have a couple of [operating systems] on one server, you can just move one of them to a second server without dropping users."