Reliability with a roadmap: choosing a tape technology to replace DDS - DDS Replacement - Industry Overview

Computer Technology Review, August, 2002 by Bill Gerstner

When DDS (DAT) technology manufacturers Hewlett-Packard, Sony, and Seagate announced they would not develop the next-generation DDS product, the DDS-5, millions of cost-conscious DDS users found themselves in need of a new tape storage product alternative. Gartner/Dataquest pinned the installed base of DDS tape drives at 6.2 million by the end of 2000 with more than 1.5 million of those units shipped that same year. (Gartner/Dataquest "2001 Industry Storage Report," Fara Yale.) The DDS replacement market was born.

Addressing the Market, Filling the Need

The DDS replacement market requires a tape technology that offers high reliability at similar or greater DDS capacities and at affordable DDS pricing levels. The replacement technology must offer a multi-generation product roadmap that meets storage growth needs while maintaining DDS price points. Those burnt by the demise of DDS do not want to relive the experience.

Will This Technology Be Around in the Future?

Before selecting a tape drive, IT managers should carefully evaluate not just individual product features and capacities, but the core technology each product is based upon. The choice will impact the organization for years to come. What is this technology's product roadmap? Is it extendible in both capacity and transfer speeds? What are the barriers to the technology reaching its full potential in future iterations? Is the company behind the technology aggressively working towards next-generation products ahead of competitive technologies?

Many IT managers chose to employ legacy tape technologies like DAT and Travan based solely on their long histories and affordable prices. The result is a frightening scenario of incompatibility between tomorrow's drives and the past decade of data, as these technologies are reaching the end of their lifecycles.

How Much Faster?

How Much Capacity?

How Much?!

Developers of new tape technologies always charge out of the gates exclaiming how much faster and higher in capacity their drives are than the competition. In doing so, a major problem is being overlooked--the price for these new tape devices can be several times the price of the servers they are backing up. Choosing a $5,000 DLT drive to back up a $1,000 entry-level server just doesn't make sense.

Finding Reliability and Capacity at an Affordable Price

In the wake of DDS, users looking to migrate from the dying technology to one of many on the market seek three core characteristics. Reliability is crucial and central to the mission of backup. Corrupt or inaccessible data negates the purpose.

As hard drive capacities steadily increase, more and more data is being stored to disk. Therefore, more and more data must be backed up. ADR2 technology brings entry- to mid-range-level server-to-backup price ratios back in line, by offering the reliability and capacity of a new tape technology at a sub-thousand dollar price point.

OnStream's ADR2 is the second generation of the company' s award winning Advanced Digital Recording technology. Achieved by coupling proven technologies with the company's continued development in advanced recording heads and tape density, ADR holds promise for several generations to come. Based on an eight-channel array head technology, ADR2 provides the ability to read or write eight tracks of data simultaneously. The data reliability is one error in 1019 bits, which is 10,000 times better than the common tape standard of one error in [10.sup.15] bits.

The exceptional reliability, capacity and performance of ADR2 technology is possible at a low cost due to four separate tape storage innovations: buried servo signaling, multi-channel recording, true variable transfer rates and enhanced data integrity.

Buried Servo Signaling Gives Precise Tape Position Information

ADR2 technology's biggest innovation is an advanced, buried servo system in the media that contributes to the highest data reliability levels of any entry- to mid-range server-backup tape device.

The buried servo system ensures data integrity by guaranteeing accurate tape tracking. During the manufacturing process, the low-frequency proprietary servo signal is written deep within the media layer. During customer use, high-frequency user data is written on top of this servo signal. The servo signal is a series of sine waves that provide precise feedback to control the position of the read/write head on each of the 384 data tracks across the width of the tape. During the read or write process, the head detects the sine waves' amplitude and phase to determine the head's lateral location on the tape and makes corrections to keep it on track.

While the head is writing, the embedded servo signal is also used to ensure data integrity. If the head detects a perturbation on the servo signal due to an off-track condition, or degradation of the signal due to loss of head to tape contact or damage to the media surface, the drive will immediately stop writing to ensure that data on adjacent tracks is not overwritten. The drive then initiates a re-write operation to ensure that the data is written correctly.