The Risk Of A Disk-Only Backup Strategy

With the dramatic reduction in the price of hard disk drives (HDD) over the years, many IT professionals are implementing disk-to-disk backup strategies to safeguard their data, and some have begun to question whether tape backup has a place in the enterprise at all. This paper considers the risk of a disk-only strategy in light of recent research into HDD reliability in real world environments, and reveals the results of a Tape Cartridge and Disk Drive Handling Test performed by Percept Technology Labs that clearly illustrates the vulnerability of disk and the superiority of tape for disaster recovery and archiving.

IT professionals have long understood that relying on a single hard disk drive is risky business. RAID, a redundant array of independent disks, is designed to mitigate this risk, and has become increasingly costeffective over time. RAID incorporates the speed of striping across several disks with redundancy through parity and failover spares to lend synergy to a system that will remain operational even in the event of individual HDD failure. As hard disk drives have become less expensive, and the use of RAID ubiquitous, the concept of disk-to-disk as a backup strategy has become quite compelling.

Disk-to-disk backup provides several benefits over tape-only backup. Virtual tape libraries on RAID provide near-line storage to ensure maximum up time. Backup to virtual tape on disk is faster than backup to a single tape drive, and faster than copying files from disk to disk - while restores occur nearly instantaneously at random access speed. Clearly, the performance benefits of disk backup make it a desirable part of a data protection plan, particularly at sites where high availability is paramount. However, any comprehensive plan must also consider disaster recovery and the need to maintain archives off-site - and in these areas, there are serious drawbacks to the use of HDDs.