Storage Basics: The Tale of the Tape


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Data backup is a universal issue that all enterprises face. Backing up to tape is the standard solution, but there is much to choose from among the available standards and options. Our latest Storage Basics article examines the tape options available for enterprises and SMBs.

Gartner Vice President and Research Director Nick Allen sees most of the action in the tape drive market coming from the upper midrange. "Far and away the strongest player there is IBM," he says.

Gartner's 2003 market share statistics support the claim. IBM and HP dominated, cornering 25% and 21% of the market, respectively. StorageTek and Quantum followed closely, with shares of 17% and 16%, in that order. Certance (formerly Seagate) took 9%, and Sony 7%. SMB-focused Tandberg and Exabyte capped off the market, registering 2% and 1.3%, respectively.

LTO and SDLT Square Off

In the active high-end midrange space favored by the enterprise, two formats compete for tape dominance: Ultrium LTO (Linear Tape Open) and Quantum's SDLT (Super Digital Linear Tape).

IBM, HP, and Certance worked together to develop LTO in 2000. LTO tapes can store 200GB of data with 2-to-1 compression. LTO's successor, LTO-2, was introduced in April 2003 and doubles that — 400GB compressed, while retaining backward compatibility with earlier LTO-1 drives. LTO-1 drives can transfer 30MB of compressed data per second, while LTO-2 drives move compressed data at 60MB per second. HP's LTO-2 flagship, HP Ultrium 460, starts at around $5,000.

Although SDLT is often criticized as a one-vendor pony, Quantum has kept it competitive. Its latest release, the SDLT 600, stores 600GB compressed. It moves data at 72MB per second, retains some backward compatibility to the DLT format, and is priced in the $4,000 to $6,000 range, similar to LTO-2-based drives.

"Depending upon when you measure it, LTO is out-shipping DLT/SDLT 2-to-1 or 1.5-to-1," Allen says. Dissatisfaction with SDLT's DLT predecessor is one reason for LTO's success. "In my user base, somewhere between 75% and 80% of the DLT users were fundamentally unhappy," Allen says.

But Allen notes a silver lining. "Another 25% to 30% said, 'Hey, this did just fine, I'd like to have some read compatibility with my existing DLT.'" Another boon for SDLT emerges at the mechanical servos level. (Servos are what reads and error corrects data from tapes.) SDLT uses an optical servo, while LTO uses a magnetic one. SDLT is advantageous for highly security-minded companies, like law firms, where degaussing tapes for security purposes is a matter of policy. "If you degauss an LTO tape, you wipe out the [magnetic] servo, and you can get it re-servo'd but it costs money," Allen says. With the SDLT's optical servo, "you can degauss it, and it's happy."

Extreme Tape Testing

Exabyte and Tandberg Data also tout LTO and SDLT drives to the enterprise, respectively, but offer other format drives to a lighter slice of the market

Exabyte positions its lower-end VXA packet technology against competitors like Sony's DDS-4 (Digital Data Storage 4) or Tandberg's SLR drives. Priced at $999, the VXA-2 drive stores 160GB of compressed data, which it moves at 12MB per second. Exabyte's VXA technology writes and reads data in packets to dodge the tape alignment contingencies typically associated with linear data transfer to create a more robust solution. To prove this, Exabyte and its customers test tapes by, in effect, torturing them and then restoring from them.

"The harshest [tests] that we've done ourselves have probably been [tapes] dunked in coffee," says Kieran Maloney, general manager of the VXA Business Unit. That test pales, however, in comparison to a test conducted by an Exabyte OEM customer. The customer pumped volcanic ash into a dust chamber with an Exabyte drive in an attempt to test until failure. "The VXA drive just kept on running for two weeks, and was reading and writing while [pumping] this volcanic ash in there 24 hours a day, and it never broke," Maloney says. After two weeks, "they just could not cause it to fail."

Tandberg also aims for robustness, but steers clear of the 'extreme sports' tape testing approach. "I suppose we could play those gimmicks; I don't know why we would," says Ken Cruden, COO for Inostor (a subsidiary of Tandberg that represents the Oslo-based company in the U.S.).

Tandberg handles problems of alignment by building more facilities into the SLR tape cartridge itself. "Both the supply hub and the takeup hub are within that cartridge and the tape path," Cruden says, "so you insert that in the drive, and you get a locking position relative to the head." This results in fewer moving parts and "extreme reliability," which is evident by an error rate of less than 1.5%, which Cruden claims is "the best in the industry." The SLR 140 is one of Tandberg's products. It holds 140GB of data, which it moves at 12MB per second compressed. It is priced in the $1,700 to $2,000 range.

Page 2: Software Considerations

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