Play it safe

By John H. MayerSpecial to GCNThe tape backup industry has a long history of new technology leapfrogging the established competition. Whether it has been reel-to-reel systems, half-inch tape, quarter-inch cassette, digital audio tape, 8-mm helical scan or digital linear tape, the questions for the user have always been the same. What is the best solution for your application today? When does it make sense to leave legacy products behind and make the jump to the next big thing?For users seeking to back up departmental and larger networks, the technology of the moment is DLT. Developed originally by Quantum Corp., DLT uses a linear recording technology on a half-inch surface and a tape length up to 1,800 feet to offer an attractive combination of capacity and durability. A single cartridge can handle more than 1 million passes across a tape head and will last up to 30 years.The first characteristics to look for in any network tape drive are recording capacity and transfer rate. Quantum's DLT line, for example, has evolved from the DLT4000, which has 20G of storage and a transfer rate of 1.5 megabytes/sec, to the DLT7000, which has 35G data capacity and a 5-megabyte/sec transfer rate. Capacity and throughput can be essentially doubled using a compressed mode.The technology's high transfer rate is credited to the use of a serpentine method of writing to the tape. Essentially, data is written on tracks that span the length of the tape. When the tape reaches its end, the drive simply moves to the adjacent track and in the process avoids rewinding.Reliability, usually expressed in specifications measuring mean time between failure, represents another consideration in any network tape drive. DLT drives, for example, typically offer recording head life of more than 30,000 hours and media durability of more than 1 million passes. Thanks to designs that rely on low tape tension and stationary heads, DLT drives will typically feature mean time between failure specifications of around 200,000 hours.The system interface of choice for most DLT backup systems is SCSI. Vendors generally offer versions of their products featuring SCSI Fast and Wide, low-voltage differential SCSI for PC servers and high-voltage differential SCSI for use with high-voltage SCSI host adapters. Vendors have begun to market high-end systems with Fibre Channel interface options for networks requiring a high level of performance and data throughput.If you need to back up a large network or are caught in the crush of relentlessly larger information requirements, automated tape backup systems offer tremendous advantages in time savings and maintenance. Vendors offer three hardware options: stackers, autoloaders and libraries.There are a number of important differences between the three options.A stacker feeds tapes in sequential order to a drive; an autoloader or library will allow random access to the cartridges. If you need to retrieve data stored on tape on a regular basis, random access capability can save time and reduce manual intervention. If your primary concern is backup, a stacker could be sufficient.Stackers and autoloaders generally feature a single tape drive and can support up to 15 tapes. Libraries, on the other hand, can support multiple tape drives and run into hundreds of tape cartridges.Accordingly, aggregate storage capacity in a library can run into multiple terabytes of data. And, because they can use all drives concurrently, libraries can back up massive amounts of data per hour. Often, a single library can replace a handful of standalone tape drives that need to be loaded manually.Given the high throughput capability, another important consideration for any automated tape library is its system interface. Even the highest-speed versions of SCSI can quickly become a bandwidth bottleneck. In many cases, your application may merit an investment in a system with a higher-speed Fibre Channel host interface.Speed also is an important consideration in the robotics of an automated tape library. Take a close look at how long it takes a library to pick, load and unload tapes. At the same time, the system's robotics will have a significant impact on reliability and durability.The question for anyone in the market for a network tape backup product today is, 'Where is the technology headed?'The answer to that question is increasingly elusive as tape storage vendors scramble to release new technologies to tap into a lucrative market with which they have had limited success'the very high-end server backup segment.Designed to expand to capacities that would allow midsize companies to mount an entire financial database on a single cartridge, these technologies promise to significantly reduce the complexity of backing up applications that traditionally have required multiple-cartridge backup systems.The competition will be tough. In one corner is Quantum with its next-generation super digital linear tape (SDLT). The company in May released the specifications for this new tape family. Rather than release one product to market and then follow it up a year later with a higher-capacity version, Quantum plans to release a series of products over a short span.First out of the gate will be a drive with a native capacity of 110G and a data-transfer rate of 11 megabytes/sec. One quarter later, the company will follow with a product that has an 80G native capacity and a native data-transfer rate of 8 megabytes/sec. And in the next quarter, Quantum expects to add an enterprise version with a native capacity of 110G or more and a native transfer rate of 16 megabytes/sec or faster.The advantage for users of SDLT will be its backward-read compatibility with the massive installed base of DLT drives. Quantum, for example, has shipped more than 1 million DLT drives, and users have purchased tens of millions of tape cartridges. SDLT is designed to provide a smooth upgrade path offering users the ability to retrieve today's archived data on their next-generation drives.Competing directly with SDLT for the high-end market will be linear tape open (LTO), a new technology that could counter the proprietary nature of DLT.LTO was designed from its inception as an open architecture available for any manufacturer to license.Built in a collaborative effort, the technology's founders are three major players in the server-tape arena'Hewlett Packard Co., IBM Corp. and Seagate Technology Inc. of Scotts Valley, Calif. In addition, Fujitsu America Inc. of San Jose, Calif., will manufacture drives, and a number of vendors have committed to manufacture media.The new tape technology will combine linear multichannel, bidirectional formats with enhancements in server technology, data compression, track layout and error correction code to boost performance.LTO's founders have announced their intention to start with two products.Ultrium will be a high-capacity, single-reel product with up to 100G of capacity and 20- to 40-megabyte/sec transfer rates. Eventually the product will evolve to 800G capacities.The second product, called Accelis, will offer fast-access, dual-reel 25G capacity and data retrieval in less than 10 seconds.Meanwhile, other vendors will push their own proprietary approaches to new performance levels. Exabyte's 8-mm Mammoth line already offers better performance than existing alternatives.And the advanced intelligent tape form factor developed by Sony Corp. of America of Park Ridge, N.J., promises to evolve to higher performance levels.The company plans to bring to market an AIT-3 drive later this year.Moreover, start-ups such as Ecrix Corp. of Boulder, Colo., offer their own alternatives for the midrange market.As with any technology, the trick for the prospective buyer will be betting which vendor will best serve his or her future storage needs.XXXSPLITXXX-