Tape storage vs. disk storage

Many prognosticators saw the emergence of fast disk-based storage systems in the early 2000s as the beginning of the end for methodical tape-based storage, but tape storage celebrated its 50th birthday in 2003 and is still looking in relatively good health. It might not be the first choice for primary storage at many businesses, but tape is typically the final resting place of loads of archived data because its cost is relatively low and it can be used to store data offsite.

"Most secondary and all tertiary storage functions and utilities, such as disk backup, transporting of large data databases and data archiving, are … best performed on tape," says a recent study from Freeman Reports. "Accordingly, tape subsystems usually accompany secondary disk subsystems to provide an optimum solution."

Not that tape is exactly thriving even in that role. Freeman estimated that tape library revenue dropped more than 15% from 2005 to 2006.

Disk's ability to back up and recover data faster at a slightly higher premium than tape has made it the preferable way to protect data. "The cost per megabyte of magnetic disk storage continues to fall, resulting in a perception that disk storage is closing the price gap with tape storage," says Freeman Reports. Some have even raised the question of whether tape really is less expensive than disk.

A recent report from the Enterprise Strategy Group shows that 21% of the respondents backed up data to disk, 51% backed up to disk and then to tape and 29% backed up to tape only.

Adding insult to injury for tape suppliers, newfangled virtual tape systems are actually disk-based systems that emulate robotic tape libraries, enabling customers to stick with a consistent data management scheme while taking advantage of disk's speed. 

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