A new trend is for companies to create mirrors of the VM volumes, says Russell, because it provides more flexibility, reduces costs and allows a company to substantiate an entire location, which fits into an enterprisewide backup strategy for disaster recovery.
For example, at the Immune Tolerance Network (ITN) -- part of the University of California clinical research group in the US -- virtualization backups have become not just a part of disaster planning, but they actually help researchers with clinical trials to fight new diseases.
ITN archives the LUN, or the specific address of the hard disk drive. Using data de-duplication algorithms that weed out redundant data, it keeps multi-terabyte archives of virtual servers. Researchers can request additional archival LUNs, a process that would be difficult or impossible with physical servers.
"The traditional method of putting a tape in a backup system serving multiple servers is outdated," says Michael Williams, ITN's executive director of IT. "Once you move to virtual storage and separation of the volume from the physical disk, you can do very interesting things. The first thing we do when we provision a LUN is we oversubscribe it. A researcher believes they have 2TB volumes -- and they do."
But in reality, the LUNs are thin-provisioned, or allocated just enough storage space on a physical disk, based on snapshot policies, and they might only be 20GB each. That volume of data is backed up every four hours. This is equivalent to a hard crash backup (a complete archive of data that can be restored to a prior state), Williams says.
Williams explains that the archives -- created using Network Appliance's SnapShot and SnapMirror -- are then moved to an off-site location and archived further using Veritas NetBackup over a wide-area network to create a full-image backup on low-cost Serial Advanced Technology Attachment drives.
He describes the snapshot process as beneficial to the researchers because it is easier to request a restore and faster than it was in previrtualization days, but it is still complex for IT. A scientist could request a data retrieval, which is similar to a traditional storage-restore request, and not have to wait for IT to access a library of tapes and make the restore. But the virtual restore process is more complex for IT, because staffers might have to, say, find and mount a virtual LUN from a restore point located on a separate backup system, such as a Veritas archive. The end user can access the data in a matter of hours instead of the much longer time frames required by tape.
Another advantage involves data de-duplication, a process in which the backup software is smart enough to see the same data multiple times and keep only one archive of it. At ITN, for example, there are 150 virtual servers, and there may be as many as 100 Windows machines. NetApp can make one copy of an identical 8.5GB image for Windows and create a fingerprint file (a reference point) for each additional archive, which saves on disk space because NetApp does not make multiple backups of the same Windows data.