Tandberg SLR Puts 'Big Punch Power' Into The DC6000 Tape Form Factor - Product Information

Computer Technology Review,  July, 1999  by Zophar Sante

• E-mail
• Print
• Link

Zophar Sante is the market development manager of Advanced Storage Products at Tandberg Data (San Leandro, CA).

Several years ago 4mm and 8mm tape technologies were "kicking sand" at the DC6000 form factor. They hoped the DC6000 would remain down for the count and keep off the beach. But the leading manufacturer of DC6000 tape drives is Tandberg Data, the same people who are building DLTtape drives, and Tandberg had other plans for this extremely popular, yet under developed form factor.

Tandberg has a 23-year history of building data backup and storage solutions and knows a thing or two about reliability, performance, and delivering value. The DC6000 is a linear tape technology and uses a large (4-in. x 6-in.) durable data cartridge. The tape drive occupies a small 5.25-in. HH footprint and has a loyal following of millions of end-users. Almost every name brand server manufacturer has and continues to ship flavors of the DC6000 form factor. In 1993, Tandberg knocked the sand off its DC6000 (Data Cartridge) tape drive and sent it into their high performance development labs for a complete rebuild. A rebuild that would position DC6000 directly against 4mm DAT and 8mm technologies.

In 1996, Tandberg launched SLR (Scaleable Linear Recording). SLR is based on the DC6000 form factor, but packed with new technology not combined in any other comparable. tape drive. By the beginning of 1999, there were seven members of the SLR family with capacities from 50GB down to 5 12MB positioned for desktop, workstation, server, and network applications. By the end of 1999, the eighth SLR drive, the SLR 100, with 100GB of compressed capacity and 10MB/sec speed will start shipping into midrange server, network, and SAN applications. That's more capacity and just as fast as the DLT7000, and 1000 times more capacity than the original DC6000.

During 1999 and beyond, analysts see SLR continuing to gain market share against 4mm DAT and 8mm helical scan for server and network class applications. In order to gain market share and the "thumbs up" from analysts, Tandberg SLR needed to not only deliver speed and capacity, but it needed to remain extremely reliable, deliver the roadmap, provide for automation, and not cost a small fortune. These combinations would provide "real" value for consultants, system integrators, and' most important--the user.

For starters--GB for GB, SLR needed to be faster than 4mm and 8mm technologies. Speed in a tape drive is not a spec on a data sheet or web-site. It's real life--hook it up to a busy NT/Intel server--and let's see what happens. The biggest problem with tape drives is keeping them streaming. Poor backup performance is generally caused when the network or server can't deliver constant data to the tape drive. if there's no data, then the tape drive has to stop, rewind slightly, and reposition forward to the point where data was last written. This process takes several seconds and, in the meantime, the server has probably recovered and is now waiting for the tape drive to be "ready." This stop/go/stop/go "shoe-shining" can go on for hours if the tape drive and the server remain "unsynchronized." This greatly decreases overall performance and a problem every tape drive manufacturer needs to address.

SLR24, SLR32, and SLR50 "Auto-Calibrate" their transfer speeds, on the fly, to stay synchronized with the server. By monitoring its own data buffer, SLR knows how well data is coming across from the server or network, SLR can lower its tape speed to "half speed" in the event the server has temporary problems delivering data at the optimum speed. Keeping SLR continuously streaming in a less than optimum environment decreases "shoe-shining" and overall backup time requirements and, thus, optimizes performance.

Another SLR 24 and higher synchronizing tool is that SLR writes "empty bytes" to the SLR tape cartridge to keep it "streaming" in the event the server becomes too busy and is not able to deliver any data for a few seconds. Not stopping and restarting every second the server has a transfer rate "hiccough" keeps SLR moving at optimum. When the server processor recovers and starts streaming data into the SLR buffer, the drive will immediately stop writing "empty bytes" and start recording real data to the SLR cartridge. This is not the case with drives that do not have this feature. With other drives, the server or network will encounter a stopped mechanism or a mechanism in the midst of rewinding and repositioning, and must wait for it to recover before it can start delivering data.

Both these SLR features are user selectable, adjustable, and enable/disable themselves "on the fly" based on fluctuations in server/network performance. With these features, "real life" independent tests prove that SLR can deliver performance that is up to 40% better than other comparable technologies. SLR delivers on the first promise--more real world performance than any other comparable tape drive.

The DC6000 form factor had an unheard of reputation for being reliable. There are millions of drives and tens of millions of data cartridges still in use today. Many of these drives were first installed when the earth was flat and 60MB was considered "monster capacity." The SLR data cartridge will maintain this long legacy of superb reliability but at 50GB or soon to be 100GB of capacity. The SLR data cartridge starts out with 4-10 times more recording surface area than its helical scan counterparts and offers a completely enclosed tape path where the media never leaves the data cartridge or is wrapped around a spinning head. Instead, the small SLR head actually glides into the data cartridge. SLR technology keeps the media contained within the confines of the data cartridge, away from any contamination. SLR brings the head to the media and not the media to the head. The media path inside the cartridge has been perfected over the past 12 years and is being used by millions of customers. The small 5.25-inch, HH, SCSI-based SLR drives have a very low moving part count. This provides resellers and users with the industry's lowest tape drive repair rate--10 per 1000. Other tape drives average annual repair rates of up to 100 drives per 1000 drives installed. SLR has only three moving parts--which means 45 times fewer moving parts than any other drive. A durable data cartridge, low moving part count, and enclosed tape path leads to a 300,000 hour uptime rating at 100% utilization, SLR delivers on the second promise--reliability.