It’s not disk vs. tape; it’s disk and tape

Posted on March 01, 2007


For most IT organizations, a combination of the two technologies provides the optimum data-protection solution.

By Chris Taylor

Recently, tape backup has received a lot of press in the technology community-much of it negative. There have been stories of tapes and data vanishing at some of the largest financial institutions, as well as other horror stories that have rippled through data centers.

With all of these incidents occurring and a more-focused look at security, many IT organizations are wondering if other alternatives are better suited for backup.

In many instances, companies have had to move physical storage devices from one location to another, such as moving a data center or part of their IT operations. In the event of a disaster, many of these organizations find it cheaper to buy new disks for data storage rather than restore data from tape. The amount it would cost the company in delays due to the recovery process makes the cost of new disk seem like chicken feed.

Anyone who has had to do a full restore, complete with incremental tapes, knows that the recovery process required for tapes can be complex and time-consuming. With downtime being public enemy number one for IT staff and management, nearline storage solutions such as disk-based backups are becoming more popular. This is particularly true for companies that are in operation 24x7, where downtime results either in loss of revenue or major disruptions in their business. (For more on disk-based backup/recovery trends, see the Special Report, InfoStor, February 2007, p. 26.)

One way to address both the need for faster restores and a solution for long-term storage and archiving of data is to use both tape and disk. For example, critical backup data is stored on disk for rapid restore. Administrators then decide how many versions of the data should reside on disk. For disaster recovery, a copy of the critical data can also be copied to tape and a second copy produced for off-site storage. Less-critical data can be staged to disk and then written directly to tape. By using this method, the data that is less-mission-critical can be staged to tape over time and the mission-critical data is available “nearline” on disk for a much quicker restore. Such things as replication from disk-to-disk, either on-site or off-site, can also be introduced for even greater availability, shortened recovery-time objective (RTO), and recovery-point objective (RPO).

Tape remains an important part of the backup solution. In most current IT strategic planning sessions, companies with significant business-critical data are looking to typically stage the data first to disk and then to tape. This means they can centralize the backup to a single tape library that can store, depending on the size of the library and the retention policies, multiple versions of the data. Rapid restores can either be done from disk for more-recent backup versions, or off the data from the library without the need to load tapes. In this scenario, a single file recovery can take fewer than four minutes.

When considering a disk-based backup solution, consider appliances that can reduce your disk-based backup capacity by leveraging compression or data-reduction techniques. Data reduction is not the same as data compression. Backup applications and tape drives both support data compression and can achieve approximately a 2:1 compression of data. But data reduction appliances can detect common patterns or chunks of data within backup files and prevent identical chunks from taking up additional disk storage space, resulting in much greater disk space savings. It’s not uncommon for backup data to be reduced by 20:1, or more, with data-reduction appliances.

One of the goals of disk-based backup systems should be to reduce the administration complexity of managing backups and restores. Once you’ve made your decision about which technology is right for you, ensure both the backup administration staff and management team incorporate the processes of this solution into their backup processes and plan accordingly for adequate testing of recovery and establishing a baseline for RTO and RPO.

Marrying both disk-based backup and tape-based backup combines the strengths of these two solutions and allows IT organizations to match the right service levels to the appropriate costs associated with the value placed on the data.

With this type of solution in place, IT organizations have the flexibility to have the right data stored on the right media that allows the optimal restore capabilities that fit the needs of the business.

Tape solutions will continue to be a vital component of data-center storage solutions in the future. Through a lifecycle data management plan, corporations can reduce costs through a combination of storage practices dependent upon their corporate policies and compliance needs. Tape isn’t dead; it has just changed its positioning in the lifecycle of data storage.

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Chris Taylor is director of professional services and sales solutions for Evolving Solutions (

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