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Xen virtualization will catch up to VMware in 2008

Alex Barrett

Virtualization is a technology in flux. Even though it has roots dating back to the 1960s mainframe, today, the term is practically synonymous with VMware ESX. Look out a few years, however, and VMware will no longer be the (practically) sole proprietor of the virtualization fiefdom, said Chris Wolf, Burton Group senior analyst, who's speaking at the Burton Group Catalyst Conference this week about "Server Virtualization: What the vendors aren't telling you."

"I still recommend the mature virtualization technologies for production use," said Wolf, but, "by the end of this year or early 2008, Xen-based virtualization will have caught up, feature-wise, with VMware."

Today, Wolf said, enterprises are actively looking at Xen-based virtualization, if not in production, then at least in their labs. "There are a lot of people who prefer the Xen architecture," he said, and they are just waiting for the platform to catch up to VMware in terms of features, reliability and manageability.

The features that Wolf expects Xen players to add to their suites include comprehensive live migration capabilities (i.e., "VMotion" in VMware parlance), better SAN (storage area network) integration and more sophisticated backup APIs.

Operating system virtualization platforms -- such as SWsoft's Virtuozzo, as well as Sun Microsystems Inc.'s Solaris Containers and IBM's newly announced WPARs for AIX -- will also start playing a more important role. "SWsoft has always been a player in

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the Web hosting space and, to a certain extent, with databases and high-performance file sharing."

Going forward, operating system virtualization, with its shared operating system image, could allow IT shops to virtualize applications that so far "for performance reasons have been precluded from running in a VMware VM," Wolf said.

Partitioning in play

Even Unix virtualization, also known as partitioning, has gotten a boost from recent interest and hype surrounding VMware. "These technologies have definitely seen a resurgence," Wolf said, and IT shops that run Unix applications "are taking a second look."

For enterprise applications such as Oracle, Unix partitioning may be the only way to take advantage of the economic benefits of virtualization. In fact, LPARs, as IBM calls them, are the only form of virtualization that Oracle officially supports, Wolf said. That is, Oracle will allow you to purchase a license that is limited to a specified partition. In contrast, if you want to run Oracle in a VMware VM, but only use a subset of the system's CPU, expect to pay for a license with the maximum number of processing cores in the system.

Unix partitioning, while it has the benefit of being a mature technology, doesn't have all of the benefits of a hypervisor. To a large extent, with partitioning, "you're still maintaining a dependency on the hardware," Wolf said. Whereas virtual machines running on a hypervisor can be moved seamlessly -- and statefully -- between hosts, operating system partitions cannot, and failover of one partition can only happen to another partition, Wolf pointed out. "That's definitely one of the downsides," he said. Therefore, if your goal with virtualization is to enable better system portability, stay away from partitioning approaches.

The hypervisor approach has its share of issues to work through, too. First of all, the industry is currently hampered by an excessive number of virtual hard disk formats. Microsoft and the Xen community espouse virtual hard disks (VHDs), whereas VMware promotes its own .vmdk format. It's still in the early days, so most ISVs don't complain about having to support both formats, but with more applications being offered as virtual appliances, this is an untenable situation, Wolf thinks.

"It's really not fair to ask an ISV to test its appliance in three different formats," Wolf said. Sooner than later, Wolf expects the various virtualization players to converge on a single virtual hard disk format -- probably through the help of a standards body like the DMTF. "I really think it's going to happen."

Virtualization's downsides

Of course, we have yet to really see the dark side of virtualization, but that doesn't mean it doesn't exist. For example, Wolf said there could come a day when digital wrongdoers turn to virtualization as a way to perform nefarious acts without getting caught. In a non-virtualized system, almost every action performed on a computer leaves a trace that can be picked up by computer forensics professionals. But imagine the combination of public access terminals and virtualization: A wrongdoer could log on, perform his evil deeds and when he logs out, all traces of that virtual session would be erased. "The only trace of wrongdoing would be the IP records," Wolf said.

Nor have hackers really begun to plumb the depths of virtualization, and that's a scary thing. "If a hacker were to write a security vulnerability that attacks a hypervisor, it could impact a lot of VMs -- or allow VMs that shouldn't be there," Wolf explained. He singles out VMware's ESX hypervisor, which is loosely based on a Red Hat Linux kernel, as being particularly vulnerable. To become more secure, "it's going to have to get a whole lot smaller." Likewise, Microsoft Windows Server Virtualization, formerly known as Viridian, also has inherent security risks. Unlike ESX, which runs beneath the operating system, Viridian runs alongside the regular Windows kernel. That has benefits such as fantastic hardware support, but being able to load any driver "is a both good and bad," Wolf said.

But even though virtualization is a moving target, don't let that scare you into holding off, he said. What with improved server utilization, portability, simplified disaster recovery, management and deployment, "the benefits of virtualization far outweigh any drawbacks."

Let us know what you think about the story; email: Alex Barrett, News Director.


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