Play it safe

Play it safe<@VM>Tape backup devices vary in their storage space, speed and price options

Digital linear tape rules the roost but new network backup technologies compete for prominence

By John H. Mayer

Special to GCN

The 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?

The DLT7 Autoloader from Benchmark Tape Systems has 280G capacity and can back up 20G of data per hour. It's priced at $4,779.

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.

No need to rewind

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.

Tale of the tape

' Stackers and autoloaders usually have a single tape drive, can handle up to 15 cartridges and are best used for small to midsize networks.

' Tape libraries support multiple tape drives and hundreds of cartridges and can use all drives concurrently, backing up massive amounts of data per hour.

' Heavy backup requirements can be too much for a library with even the fastest SCSI connection; managers of large enterprises may want to invest in a system with a Fibre Channel host interface.

' Faster systems with high capacities are just around the corner, though which of the competing technologies will emerge as the leader is anyone's guess.

Library privileges

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.

The next big thing

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.

The 230D from Exabyte uses DLT technology to supply 1.05T of storage and can back up 36G of data per hour. It's priced at $19,995 to $20,745.

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.

John H. Mayer of Belmont, Mass., writes about information technology.

VendorProductMediaNative capacityBackup performance per hourInterfaceMean time between failure, in hoursCommentsPrice
Redmond, Wash.
DS9000 SeriesDLT4000 DLT7000 DLT800080G43GSCSI-280,000Basic external tape backup for network servers, with integrated LCD$3,595 to $6,895 up
Tape Array 5same400G216GSCSI-2 LVD/SE or HVD80,000Rackmount system with up to 5 drives, hot-swap drives, redundant fans, power supplies$2,650 up
FastStor 22same1.76T43GSCSI-2 LVD/SE or HVD80,000Autoloader with 22-tape capacity, small footprint$7,995 up
Scalar 458 Seriessame4.6T172GSCSI-2 SE or HVD80,000Scalable libraries supporting up to four drives and 48 cartridges$31,647 up
Scalar 100/DLTsame4.8T260GSCSI LVD/SE or HVD Plug-in SAN module250,000Highly scalable library supporting up to six drives and 60 cartridges, with multiple connectivity options$11,310 for unit, $8,670 per drive
Scalar 1000/DLTsame63T36GSCSI-2 differential200,000 (drive)Automated library for data center supporting up to 48 drives and 788 cartridges$14,950 for unit, $10,600 per drive
AIT 70/100AIT-1 or AIT-2100G43GSCSI-2 LVD/SE or HVD200,000 (drive)Designed for workstations and small networks; has integrated LCD$33,395 up
Scalar 1000/AITsame118.2T43GSCSI-2 differential200,000 (drive)Is highly scalable for data center applications, supporting up to 12 drives and 237 cartridges$49,950 for unit, $13,859 for two drives
Benchmark Tape Systems Corp.
Boulder, Colo.
DLT1DLT40G20GWide Ultra SCSI LVD200,000 (drive)Basic system in internal or external configuration$1,499
DLT7 AutoloaderDLT280G20GSame200,000 (drive)Autoloader for midrange systems with seven-cartridge capacity$4,779
Breece Hill Technologies Inc.
Boulder, Colo.
B1 DLT1DLT40G21.6GSCSI-2 LVD/SE200,000 (drive)Drive for small networks$1,499
Q2.15DLT600G43GSCSI-2100,000Basic tape library configuration supports two drives and 15 cartridges$6,550
Q6.100DLT4T130GSCSI-2 HVD250,000Scalable system supports up to six drives and 100 cartridges$31,972
Q.18.280DLT11.2T389GSCSI-2 LVD/SE or HVD100,000System for data-intensive applications supports up to 18 drives and 280 cartidges$81,837
Ecrix Corp.
Boulder, Colo.
VXA AutoPakVXA-1445G18GSCSI-2 LVD300,000Low-cost, entry-level tape library$4,495
Exabyte Corp.
Boulder, Colo.
Mammoth-2 (M2)Mammoth-2 8 mm compatible60G43.2GSCSI, LVD FC300,000High speed drive for midrange networks; self-cleaning$4,995 to $5,395
Mammoth-LTMammoth LT 8 mm compatible14G7.2GLVD SCSI single- ended, narrow SCSI250,000Economical drive for high-speed applications$1,617 to $2,036
MammothMammoth 8 mm compatible20G10.8GSCSI-2250,000High-speed drive for large departmental networks$3,420 to $3,995
Eliant 8208500 series 8 mm7G3.6GSCSI-2 single-ended or differential200,000Drive for midrange networks$1,590 to $1,955
230DDLT1.05T36Gsame200,000Tape library supports two drives and 30 cartridges$19,995 to $20,745
X80 Mammoth-24.8T346GSCSI HVD, LVD250,000High-performance tape library supports eight drives and 40 cartridges$32,685 to $37,680
Hewlett-Packard Co.
Palo Alto, Calif.
DLT 40DLT20G5.4GSE, narrow SCSI-2 SCSI-3200,000Drive for midrange networks includes firmware diagnostics; comes in internal, external or rack-mount units$2,905 up
DLT 80DLT40G21.6GSE, Fast Wide SCSI, SCSI-3250,000Drive for enterprise applications features high transfer rate, LVDS connectivity$5,681 up
Quantum/ATL Products Inc.
Irvine, Calif.
PowerStor L200DLT280G180GSCSI-2200,000Cost-effective system for departments and workgroups; has one drive$5,999
PowerStor L500DLT490G54GSCSI-2200,000Supports up to three drives for small to midsize LANs$11,120
P1000 SeriesDLT1.05T72GSCSI-3250,000Library for midrange applications supports up to four drives and 30 DLT cartridge slots$18,900
7100 SeriesDLT3.5T126GSCSI-3170,000For multiterabyte applications, supports up to seven drives and 100 cartridges$39,875
P3000DLT11.T288GSCSI-3250,000For online transaction processing, data warehousing, image archiving applications$89,970
P6000DLT22.8T576GSCSI-3, FC250,000Enterprise system supports up to 32 drives and 652 cartridges, with Fibre Channel interface$220,325


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