Disk Vs. Tape: Who's Got Your Back?

In their push to change the way corporate data centers back up their data, the vendors often leave in their wake confusion as to the viability of hard disk as a tape substitute.

However, the tape automation market remains strong and may even grow despite--or even as a result of--the growth of disk-based backup systems, solution providers and analysts say.

Such systems come in two flavors. Disk-to-disk backup subsystems cater to companies looking to either back up data exclusively to disk, or back up the data to disk as an interim step before sending it to tape later. Disk-to-disk-to-tape subsystems come integrated with a tape backup system or are designed to be easily integrated with tape.

Data can be backed up to disk-based subsystems in one of two formats: The original files either are copied or are streamed in a format matching tape technology formats such as LTO and SDLT.

Disk-based backup arrays are not displacing tape for the most part, said Robert Abraham, president of research firm Freeman Reports. "In some cases, they do, but they really make tape backups more user-friendly, and so they make it easier to use tape," he said.

Actually, disk-based backup arrays make users more likely to back up to tape, Abraham said. Instead of tape sales falling, the latest Freeman report on compact tape drives, which include cartridge, DAT, 8mm, SAIT, DLT, SDLT and LTO drives, said shipments are expected to hit 2.2 million units this year, up 5.2 percent over last year. By 2009, the market is expected to hit 2.9 million drives.

In another soon-to-be-published study by Peripheral Concepts, Farid Neema, president of the consultant firm, said about 10 percent of more than 600 surveyed enterprises stated they use 50 percent or more of their hard-drive capacity for data backup and archiving. Paul Noe, senior solutions architect at Unicom, a Woonsocket, R.I.-based solution provider, said the tape market is at worst staying flat. "Customers use disk for the fastest backups and high-speed data access," he said. "But they will always keep copies [on tape] off-site to be safe, or for disaster recovery."

In addition to backups and archiving, tape"when combined with various types of disk-based backup subsystems--also is a critical part of a data center's compliance technology, said Todd Holcomb, director of business assurance services at Evolving Solutions, a Hamel, Minn.-based solution provider.

There is no ROI in technology related to keeping data online after a year, by which time it may never be accessed, said Holcomb. "Until the day comes when disk can be equal to or less than tape in price, and disk capacity is greater than tape [capacity], tape will never go away," he said.

Organizations concerned about data availability will want to back up to disk and tape, said Greg Knieriemen, vice president of marketing at Chi, a Cleveland-based solution provider.

That, plus a recovery in the economy and IT spending, have combined to increase interest in enterprise tape, Knieriemen said. "We are selling full solutions," he said. "Last year, customers might talk to us about tape. Now they are talking about a SAN with a tape solution."

Thomas Thompson, an account executive at Quest, a Sacramento, Calif.-based solution provider, said disk-based backup solutions are definitely on the rise. "No one will argue about getting faster restores," Thompson said. "Instead of waiting for [a data storage company] to bring back their tapes, [users] can pull the information off a hard drive."

However, while some customers believe disk-based backup systems mean tape can be tossed from the data center, others realize that tape is still necessary for long-term and regulatory storage, Thompson said. "Tape can help eliminate errors. With disk, you can still have a spindle fail."