Storage-area network vendor Sanbolic is giving VMware virtual machines the ability to share access to application data, eliminating one source of complication that arises when IT shops move virtual servers among physical machines.

The inability of virtual servers to share application data is common across all major virtualization platforms, resulting in inflexible SAN storage platforms, according to Sanbolic. (Compare storage products.) The vendor announced this new capability for its Melio clustered file system Wednesday at the Microsoft TechEd conference in Orlando. 

Without shared access to application data, IT shops have to manually remap data when they move an application from one server to another, says Bill Stevenson, Sanbolic's executive chairman. "In a very large environment it adds one more step and one more piece of complexity," he says.

More importantly, says Gartner analyst Raymond Paquet, Sanbolic's updated software allows multiple people to access and write to the same file.

"Virtualization is creating the opportunity to have things shared at its base," Paquet says. "You're sharing multiple operating systems or multiple applications now on a single machine. What Sanbolic is doing is allowing you to share a file system. So it's further down the stack."

The new product, which is designed specifically for VMware, is called Melio Clustered File System Application Data Solution for VMware ESX. VMware's hypervisor stores virtual machine images in a shared SAN volume, according to Sanbolic. But application data – for example, the e-mails in Microsoft Outlook or the content of a Web site – must be uniquely assigned to a single virtual machine.

"This inflexible storage/server coupling means that there is a single path to the data, and data cannot be easily shared to scale out applications or for multi-tier applications," Sanbolic states in a PowerPoint presentation.

Recovery from failure is another issue, according to Stevenson. If a virtual server that's mapped to a particular storage volume fails, no other server can immediately access the data, he says. But Sanbolic's new software lets them all access the data even if one fails.

"With a typical SAN without a clustered file system, you don't have the ability to have concurrent access to the application data from the Web server and from the other servers that are creating content," Stevenson says. "With our clustered file system you can have five Web servers all accessing the same content on the shared SAN storage volume."