Tape isn't as popular a medium for backup as it was a few years ago, but when it comes to long-term archiving, it still has long legs.
There's no doubt about it, "if you're just looking for pure archiving, tape has [disk] beat hands down," says Bruce Master, senior program manager for worldwide tape products marketing at IBM, which is a founding member of the LTO Consortium. The consortium is promoting the availability of its LTO-3 WORM cartridges, which can store up to 800GB of compressed data in a compliance-friendly format for approximately $.16/GB. From a raw media cost perspective, pricing for 800GB of
Serial ATA (SATA) disk drives comes to approximately $.65/GB.
Over the long term, tape's price advantage is actually much greater. A recent white paper by Data Mobility Group, Nashua, NH, titled "Is tape really cheaper than disk?," finds that over seven years, the cost of maintaining data on disk rather than tape is almost an order of magnitude higher.
Specifically, Dianne McAdam, partner and senior analyst at the Data Mobility Group, compares the cost of storing a 50TB data set growing at a rate of 20% per year on a generic SATA array vs. a four-drive LTO-2 tape library. Factors McAdam considers include hardware and media costs, utilization rates, compression and environmental costs such as power, heating, cooling and floor space. At the end of seven years, she found the total cost of ownership for disk to be $2,105,368 vs. $231,163 for tape.
The latest vendor to recognize tape's appeal is, of course, Sun Microsystems, which last month announced it would acquire StorageTek for $4.1 billion. But the company has been talking up tape for much longer. Earlier this spring, Sun announced its Content Infrastructure System (CIS), which includes servers, a hierarchical storage management file system, Fibre Channel and SATA disk and, naturally, tape.
"The length of time you need to keep [data] now dramatically exceeds the life of the medium," says Chris Wood, director and chief technologist of Sun's data management practice. "That's brought on an unprecedented requirement for change in how we build storage devices and store data on them." Tape, at one-twentieth the cost of disk by his estimation, is an integral component of any long-term archive strategy.
Expect to hear a lot of tape talk from Sun, which is enamored with its economics. In his recent blog, Sun president and COO Jonathan Schwartz asks, "Is tape sexy?" The answer: "Is five-nines availability sexy? How about $1/cpu hour? Price performance is sexy."