Typically, virtual appliances consist of a pre-configured application stack and an operating system. Examples of applications that have shipped as virtual appliances include collaboration, email security, firewalls, intrusion detection and traffic management.
Linux can also often be found in a virtual appliance. Its appeal is that it can be freely distributed alongside the application.
In a twist, last month, Red Hat Inc. and VMware Inc. partnered to distribute a RHEL5/VMware Server bundle as a virtual appliance through the VMware Virtual Appliance Marketplace. Sun Microsystems Inc. is also distributing OpenSolaris as a virtual appliance.
For IT managers, the main benefit of an appliance is faster set-up times, said Javier Soltero, co-founder and CEO of San Francisco-based Hyperic Inc., which is considering distributing its open source Hyperic HQ systems management suite as an appliance. "We mentioned to a potential customer that we work hard to keep installation time under thirty minutes. The customer said 'That's 29 more minutes than I would have spent if it were an appliance,'" Soltero said.
But, while many IT managers may be tempted by virtual appliances, first they should try and understand their limitations, said Peter Christy, co-founder of Los Altos, Calif.-based Internet Research Group.
Upgrading the appliance
"The problem with virtual appliances is they really do not address functionality upgrades or system vulnerability," like a crippling buffer overflow, Christy said. "It's a frightening world we live in, and when that kind of problem is discovered, it creates a real urgency to get a patch from the vendor."
Virtual appliances do not negate IT managers' responsibility for securing their applications. Just because an application comes as a virtual appliance doesn't mean it is immune to exploits. "[Virtual appliances] are something to look into, but there are a whole bunch of applications where a lot needs to be done," he said.
Red Hat had an answer for Christy's concerns. Scott Crenshaw, a senior director of product management, said IT managers benefit from virtual appliances because they represent a standard environment in which to run applications.
"When [IT managers] have a problem, the traditional model requires them to isolate a problem, characterize it and then get help from their support provider," Crenshaw said. "By having a guest OS integrated with the application, it is much easier to test and prevent those security vulnerabilities to begin with."
Crenshaw also addressed Christy's security concerns. "With a virtual appliance, we deliver [everything] as one package. If there are issues down the line, Red Hat issues an entirely new package. It's as close to instantaneous as you can get," he said.
Crenshaw said administrators won't have provisioning headaches with virtual appliances either. The challenge of matching up applications, hardware and the operating system would be irrelevant. The virtual appliance just doesn't care, he said.
Boatloads of bits
But there is a small price end users do have to pay for the convenience of an appliance -- the size of the package, said Hyperic's Soltero. For example, Hyperic bundles are usually about 80 MB to 100 MB in size. Creating an appliance complete with an underlying OS would increase the size of the bundle by a factor of four to five, (i.e., 320 MB to 500 MB).
"For a downloadable product, an appliance is a pretty big bundle," said Soltero. "It's a horse race between how long it can take to download the appliance, and how long it takes to just download the bits."
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