Data protection: recovery with tape

Computer Technology Review, Oct, 2004 by Rich Harada

The Least Common Denominator

In designing a system of any type, where there is a range of requirements that need to be met to satisfy a number of diverse customers, it always helps to start at the least common denominator and then add where necessary to satisfy the more demanding requirements.

"In the case of a data protection/business continuance plan, the common denominator should be an automated tape solution," says Bob Raymond, StorageTek's manager of Tape Product Engineering. "Tape can protect any and all data classes, and provides an easy and inexpensive means for transporting data to an off-site location for disaster recovery purposes."

A tape-based backup program, where tape sets are routinely cycled to a remote location and then returned for reuse, offers the best combination of fast local data recovery (when specific files or systems are lost), remote data recovery (when there is a data center outage), and overall cost. And despite the creative claims made by some vendors in the disk-based backup business, the total cost of acquisition and ownership (TCO) of tape is still a small fraction of the TCO of any disk-based solution. (See "Is it Tape and Disk or Tape versus Disk?", June 2004, CTR.)

Tape Protection and Data Access

Tape-based solutions may be supplemented by disk-based technologies to improve system performance for those applications that require it. Although tape may be fast enough to move data from point to point, the combination of technologies may provide a better total protection solution.

For example, an application that cannot tolerate any downtime or loss of data would be a candidate for clustered servers and mirrored storage to protect against device failures. A once-per-day backup on tape would not satisfy this requirement by itself. But a disk mirror does not protect against data deletions (when a file is deleted, it is simultaneously deleted from both sides of the mirror), nor does it protect against power outages or other disasters that shut down the data center. Instead, a combination of disk mirroring and tape backup can provide a more complete protection scheme. The mirror can take over if the primary disk drive fails, and the backup tapes can be used to recover specific data files or provide the full backup data set needed if, say, a virus corrupts the entire storage array.

In another example, such as an e-mail server for a global organization, where the availability of time to perform backup operations is extremely limited, a disk-based backup solution can provide for smaller backup windows, and also provide somewhat faster recovery of distinct data files. But again, a disk-based solution does not provide off-site protection and, therefore, normally feed their data to a tape system for offsite transport and longer-term retention to meet compliance mandates.

Lastly, user systems including desktops and laptops need to be protected, especially in businesses that employ a large number of computer users. "Copying data files from network-based user systems to a backup server, which then streams them to a tape system, is the most cost-effective solution to meet data protection requirements for this asset class," says Jim Milligan, Imation's executive manager of Tape Strategy. "Using any additional protection layers for this asset class might be a waste of money."