Backing Up the Virtual Machine

Server virtualization demands a multilayered approach to storage.

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Charles Keiper, senior NetVault product manager at BakBone Software Inc. in San Diego, says he hasn't seen any changes as a result of the EMC buyout and doesn't expect to. "In the long term, they may provide some level of integration we can't match," he says. "But I do not see them changing the current model, because it would restrict the growth of VMware if they restricted the ability of products to interoperate."

Backup for All

Backup vendors are ensuring that the latest versions of their software can address both physical and virtual machines, and from an administrator's viewpoint, there is often no difference.

"For the most part, a virtual machine works and acts the same way a physical machine does," says Bob Roudebush, director of solutions engineering at NSI Software in Hoboken, N.J.

But the backup software has to treat the virtual machines differently. For one thing, there is the matter of resource consumption. Running multiple virtual servers on a single physical server results in better resource utilization during normal operations but can saturate those resources during backup.

"The problem is compounded when you have multiple virtual machines competing for resources from the host system during backup cycles," says Tricia Jiang, technical attache for IBM Tivoli storage systems. "Backups from one virtual machine can starve resources from applications running in other virtual machines." To address this, Tivoli Storage Manager can stagger the backups across low-peak windows.

Then there is the matter of what to back up -- each virtual server individually, or the physical server on which they run. Syncsort Inc.'s Backup Express lets users select either mode.

There is also the option of backing up the entire virtual server as a single file. "This method requires fewer backup agents on the virtual machine but is not application-aware," says Kelly Harriman-Polanski, director of product marketing at CommVault Inc. in Oceanport, N.J. "It also requires backup of very large files, which are typically 2GB in size or larger, unless the administrator takes the time to execute an export command to convert the file and zero-out the unused portions of the file."

According to Brian Wistisen, senior product manager in Symantec Corp.'s data management group, the main challenge lies not with the backup itself, but with the process of converting between the virtual and physical environments. "This is where many solutions face the realities -- and dependencies -- of dealing with all the various low-level hardware devices and drivers necessary to operate the system effectively," he says, "particularly when converting from a virtual state to a physical one."

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