When it comes to backing up virtual servers, IT administrators have a lot of choices. But increasingly, they're finding one method of backup isn't enough to satisfy all the demands of a virtual environment.

Some are opting for a combination of methods, such as using agent-based and serverless backup for protecting data on virtual machines, then using cloning or snapshot technology for protecting and recovering server images in the event of a hardware failure.

For instance, Ben Moore, a systems engineer for Mission Hospitals in Asheville, N.C., uses a multilayered approach.

Moore has had VMware ESX Server installed since October 2006 on 10 physical servers with 60 virtual machines. His method of choice is VMware Consolidated Backup (VCB) in combination with Tivoli Storage Manager.

"We use VCB piggybacked on our existing Tivoli Storage Manager backup software," Moore says. "You put your backup software on a proxy server that is aware of the storage space for your virtual machines, and then the VCB integration scripts allow you to have visibility of your virtual machines and that storage."

Michael Passe, storage architect for Beth Israel Deaconess Medical Center in Boston, likewise uses a multilayered approach.

Passe has 10 VMWare ESX servers hosting about 100 virtual machines. He uses Vizioncore's esxRanger once a week to capture the Virtual Machine Disk Format (VMDF) image-level backups. (The VMDK describes the format and storage of the file containing the virtual machine instance.) He also uses Symantec Veritas NetBackup agents on Linux and Windows guest operating systems daily for file-level restore capability.

Passe is testing VCB.

For his part, Robert Berry, director of technical services for magazine publisher Homes & Land in Tallahassee, Fla., has been using Swsoft's Virtuozzo for a year to virtualize 15 physical servers into 39 virtual private servers.

"We span our virtual machines across two separate hardware nodes. If one was to crash, we just clone from the one and bring it over to another," Berry says.

"I do a normal backup of the Progress database with the Progress backup tool. I back up the Progress database to the virtual machine, and then back up the virtual machine using Virtuozzo's Management Console and vzbackup utility," Berry adds.

At Springfield Technical Community College in Springfield, Mass., backup technology is critical to providing a safe environment for students to learn about operating systems.

Sam Jamrog, an adjunct professor at the college, uses VMware workstation to teach students about Linux and security. "We have about 25 machines with VMware workstation installed," Jamrog says. "All my Linux students have a virtual Linux machine on their Windows XP host."

Jamrog says one of the biggest difficulties in teaching students about operating systems is the fear of ruining the system. Backup utilities can help minimise that fear.

"We use snapshots [a capability included in VMware Workstation] to keep several images of the OS on their system," Jamrog says. "It takes a few minutes to create a snapshot, but only seconds to restore a broken machine. That way they can fearlessly make changes to their virtual machines, and if they do have a problem they can simply revert back to a working system."

"For security my students will clone several machines and create a 'virtual network' of operating systems. They will also make snapshots just in case they do damage to a virtual machine. This way they can practice security scans on a virtual network locked off from the school network, without much fear of getting into the school network by mistake," Jamrog adds. "They can get as aggressive as they want with the security scans, as any problem they create is one click away from being fixed in seconds."