VMware Inc. gets the lion's share of the attention around virtualization, but at least one user of SWsoft Virtuozzo, an operating system virtualization platform, says that going down the Virtuozzo path afforded his firm significant savings over VMware.
John Yanekian, director of network services at the National Association of Home Builders (NAHB), a trade association in Washington D.C., was using VMware GSX (now VMware Server) two years ago, but switched to Virtuozzo because of operating system license costs.
"It wasn't about performance, but TCO," Yanekian said. "What VMware was doing was loading in to an OS then running the VMs on top, and each OS had its own environment," he said. "Each and every [Windows] instance we installed needed its own license."
"VMware is great because you have a lot of flexibility to run NT and Windows 2003 – whatever – at the same time, but you pay for that flexibility," he said.
Virtuozzo, in contrast, only allows you to run a single operating system (OS) flavor. It works by creating an isolated partition – or virtual environment (VE) in Virtuozzo parlance -- off a single baseline OS. Because of that, SWsoft told Yanekian that NAHB would only have to buy a single Microsoft Windows Server license per host. On a machine with 10 guests, "instead of 11 Windows Server licenses with VMware, we only had to buy one," Yanekian said.
Of course, since then, Microsoft has changed and clarified its licensing policies for Windows Server instances running within virtual machines. Today, a single Windows Server Enterprise Edition license grants the right to run four instances of the OS, while Datacenter Edition allows an unlimited number of guests. At the same time, SWsoft has stopped advertising the licensing benefit Yanekian enjoyed when he purchased Virtuozzo, and publicly states that SWsoft customers must license all individual Windows instances running on top of Virtuozzo.
Not everyone, however, has gotten the message. "Microsoft only changed its licensing/clarification of the licensing only recently (and after NAHB bought Virtuozzo) and it is not easy for customers to keep up with all the changes," wrote an SWsoft spokesperson.
Even so, choosing Virtuozzo over VMware would still save NAHB money today, even if Windows was properly licensed. NAHB currently runs three Virtuozzo hosts – two in production, and one for staging. The production environment runs with 18 VEs running across the two production boxes. If NAHB were using VMware, that would require a minimum of five Enterprise Edition licenses, rather than just two.
For server hardware, NAHB runs on SAN-attached dual-processor Hewlett-Packard DL380s with 8GB of RAM. Applications ran the gamut from SQL Server 2005 to ACT! to Filemaker Pro. NAHB did have trouble running one application within a Virtuozzo VE, which Yanekian attributed to its need for a specialized video driver.
Differences with VMware
A common complaint about operating system virtualization is that it doesn't provide the same level of isolation between guests as a hypervisor-based approach such as VMware ESX.
"If you have a kernel fault, that will bring down everything on the system," said Gordon Haff, principal IT adviser with Illuminata in Nashua, New Hampshire. "In principle, you could also have a fault with a hypervisor, but the theory is that a hypervisor is much simpler and that's its much less likely."
But Yanekian hasn't had any trouble with misbehaving OS instances, and he can manage each instance separately by customizing their individual registry files. There is a catch of course – all the guests must be on the same service pack level -- but "that's not a problem for us," Yanekian said, as he prefers to keep all his servers on a "cookie cutter standard build."
Basing all your servers off the same service pack does have its management challenges. For one thing, Yanekian said, "we don't apply Microsoft security updates." Instead, NAHB relies on a Virtuozzo update services from SWsoft. And moving VEs between hosts isn't as quick with Virtuozzo as it would be with VMware and VMotion. With Virtuozzo, it is possible to make a copy of a VM and restart it on another host, but the copy of the VM doesn't appear instantaneously after the restart.
However, Yanekian said that NAHB has also derived other cost savings from virtualization. "We don't buy as many development servers anymore. Every time someone needs a new server, we ask them if they can use a virtual server instead."
Virtuozzo is currently available for both 32- and 64-bit Windows, plus a variety of Linux distributions running on x86, ia64, AMD64, EM64T, and Itanium chips. Pricing starts at $1,250 per socket. Other examples of operating system virtualization software include Solaris Containers, a.k.a. Zones and the open-source version of Virtuozzo, OpenVZ.
The area where operating system virtualization has traditionally shined is among hosting providers, said Haff. There, the ability to run only a single operating system version isn't a liability – it's an advantage. "Hosting providers want to run only one copy of the OS," he said. "The disadvantages of OS virtualization don't really apply to them very much."
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