Evaluating the total cost of ownership (TCO) of any storage purchase is always important. But when it comes to integrating disk and tape, the TCO choices can be challenging -- particularly as vendors pit the two technologies against each other.
Recent research done by the Tape Technology Council, a non-profit trade association composed of tape vendors, pointed out common overlooked costs of storage purchases, including power and cooling, floor space, security and personnel training.
"There's a lot of focus on hardware and media costs, installation, controllers and application software to arrive at a comparative cost-per-gigabyte," said Tape Council President Rich Harada, adding that these "up-front costs" are only part of the picture. "By examining other factors that can play a role in the long term, the true advantages of one system over another become clear," said Harada.
Not surprisingly, the Tape Council is partial to the TCO advantages of tape. The council's study compared one user's TCO results for tape, optical disk and magnetic disk over a three-year period by looking at costs for hardware, software/controllers, media, hardware/software maintenance, floor space and power consumption. Their research ultimately showed tape to have the lowest initial cost and the best overall value of the three technologies. The study revealed the following total costs over a three-year period:
Jim Damoulakis, CTO of GlassHouse Technologies, Framingham, Mass., agreed that operational costs like floor space and power consumption, and not just the cost of equipment, should be considered when making a purchase. But he added that although tape is cheaper on a cost per GB basis, disk offer cost benefits by easing the amount of nightly backup problems.
"A problem with tape is data sometimes can't be fed to the tape drive fast enough and the tapes slow down or stops, wasting time and money," said Damoulakis. "Tape is cheaper, but a company has to figure out how much they value the predictability and reduced amount of management that comes with disk."
Bart Bartlett, director of marketing at disk-based backup vendor Data Domain, said that disk is more expensive than tape until you factor in data compression. "Our disk storage system compresses data to a compression ratio of 20 to 1. That can drive the cost of disk down to be competitive or even lower than tape."
Both disk and tape suit different applications, but the ones that are growing are a better fit for disk, according to Kevin Daly, CEO of Avamar, another disk-based backup software vendor. "Most people have all the tape they'll ever need if they evolve towards a mix of both disk and tape," he said.
Diane McAdam, a partner and senior analyst at the Data Mobility Group Inc., Nashua, N.H., doesn't see the TCO debate as an either/or issue. She acknowledged that a 100% tape solution is much cheaper than a 100% disk solution, but it really depends on what technology a company needs. "If I'm an IT guy at a financial firm and there are transactions that can never be lost and need to be retrieved quickly, I would use disk-based remote replication. I couldn't possibly use tape for that."
McAdam did agree that in addition to hardware and software maintenance costs, disk will cost more over time because of the higher turnover rate of disk equipment. "Disk technology tends to get refreshed every two or three years, where tape libraries get replaced every five to seven years."
Harada noted that although the tape council's research showed that tape has a better TCO, one technology can't stand alone. "Disk may be right for certain applications even at a higher cost, but it still isn't a complete data protection solution. It still should be backed up with tape."
Added McAdam: "Maybe making tape and disk a religious war is more exciting, but it shouldn't be that way."