Fara Yale, April Adams Technology Overview 27 August 2003 Tape Drives: Overview Summary With the wide variety of formats and technologies available today, tape drives continue to be the technology of choice for backing up and archiving data, delivering the lowest cost per megabyte stored. Table of Contents Technology Basics Linear Technologies Helical Scan Technologies Tape Automation Products Technology Analysis Business Use Technology Leaders Recommended Gartner Research Insight Gartner Reproduction of this publication in any form without prior written permission is forbidden. The information contained herein has been obtained from sources believed to be reliable. Gartner disclaims all warranties as to the accuracy, completeness or adequacy of such information. Gartner shall have no liability for errors, omissions or inadequacies in the information contained herein or for interpretations thereof. The reader assumes sole responsibility for the selection of these materials to achieve its intended results. The opinions expressed herein are subject to change without notice.
Technology Basics Mainstream tape technologies are aligned within two camps linear recording and helical scan recording. The debate over which technology is better suited to safeguard an organization s valuable data assets usually centers on reliability, compatibility, capacity and performance. When at odds in competitive situations, each technology claims advantages over the other in each of these critical metrics when in fact both technologies are well suited to meet the requirements of a majority of computing environments. Linear Technologies Linear tape recording technology has been in use since the early stages of computing. It was initially used as a primary data storage medium as an extension of central processor memory. As storage requirements changed, however, it was replaced in this role by hard disk drives (HDDs), which provided the advantage of random access capability. Applications for tape in the computer world then evolved to encompass data backup, data archiving and data interchange or distribution, and the role of tape drives and tape media transitioned to that of secondary storage. Over the years, linear tape technology has evolved in all key areas capacity, performance and reliability and drives based on linear recording remain the leading secondary storage device for today s computing environments. There are several tape technologies that fall into the linear technology category: quarter-inch data cartridge, minicartridge, DLTtape, Super DLTtape, Linear Tape-Open and high-end half-inch cartridge technologies, such as StorageTek s 9840 and 9940 and IBM s Magstar. Each one is discussed separately below. Quarter-Inch Cartridge Quarter-inch tape technology was introduced more than 25 years ago, and although market share has declined in favor of new formats that yield higher capacity and performance, quarter-inch drives still account for a large installed base of primarily smaller networked and stand-alone environments. The technology has evolved into higher-capacity implementations, and it has established standards for backward compatibility that have contributed significantly to its long life. Quarter-inch data cartridge tape drives use media that is 0.25-inch or 0.315-inch wide and comes in various lengths. The widening and lengthening of the tape were developments that contributed to moving the technology to new capacities. Data is recorded in a linear serpentine fashion on tracks that are parallel to the edge of the tape. Each 1/4-inch tape cartridge contains two reels, one for tape supply and the other for tape take-up. The tape guides and the tape path are also internal to the removable cartridge. Tandberg Data became the sole drive manufacturer in this segment in 1999 with its Scalable Linear Recording (SLR) technology, which the company (in partnership with Imation), continues to develop. Tandberg sees its SLR series as positioned in the entry-level and small-to-medium business segment and scaling into the midrange multiuser segment of the market. With the introduction of the SLR100 in November 1999, Tandberg Data laid the foundation for its third generation of SLR tape technology. The newer drives the SLR7, SLR60 and SLR100 share a common mechanical platform, the same firmware and the same method of encoding and decoding data. This allows SLR technology to scale in capacity and performance while maintaining backward compatibility and reducing product cost. Other details on the three drives common and differentiating features include: Read Channel The SLR7, SLR60 and SLR100 drives use a Partial Response Maximum Likelihood (PRML) channel encoding technology which was developed by Overland Storage (formerly Overland Data). Tandberg and Overland announced a cross-licensing agreement in April 1998 that made Tandberg the first company to license Overland s Variable Rate Randomizer (VR2). VR2 is a PRML 27 August 2003 2
data-encoding/decoding technology developed specifically for linear tape drives. It is designed to increase the capacity and performance of a product or technology by a factor of 1.5 to two times. Other companies will also implement this technology. Multichannel Thin-Film Magneto-Resistive Head (TFMR) The SLR100 and SLR60 both use a sixchannel TFMR head. The SLR7 supports a two-channel TFMR head that writes two tracks at a time. The use of TFMR head technology, coupled with VR2 encoding techniques, doubles the tape capacity when compared with previous-generation SLR drives. Dedicated Servo Tracking The SLR100 and SLR60 utilize a servo-based track-following system. The dynamic real-time servo tracking is designed to allow the drive to reliably record and recover data at high-track densities. The SLR7 uses prerecorded reference bursts for head alignment instead of the dedicated servo tracks used on the SLR60 and SLR100. The SLR60 and SLR100 record on 192 data tracks, and an additional 24 tracks are used for servo positioning. The SLR7 records on 72 tracks and uses 18 reference bursts for head alignment. Auto-Sensing Variable Data Transfer Rate The SLR100 and SLR60 support an auto-sensing feature that assists in performance optimization. This auto-sense feature automatically adjusts the drive s data transfer rate from the host to the drive s buffer. Optimizing the transfer rate helps to keep the drive s data buffer full and keeps the tape moving at a constant speed, thus minimizing the number of times that the drive must stop and reposition itself before resuming read/write operations. In those instances when the data transfer speed from the host does fall below the minimum transfer rate for the drive, the drive will empty its buffer while quickly repositioning itself at the same time so it is ready to resume write operations once the host fills the drive s buffer. In-Line Data Compression Data compression technology used in Tandberg s SLR drives is based on the Adaptive Lossless Data Compression (ALDC) algorithm. The SLR100, SLR60 and SLR7 all support an updated compression scheme called in-line hardware data compression, which allows data to be compressed before entering the drive s 8MB buffer, thereby minimizing backup and restore times. By using a separate data compression path, 100 percent of the drive s buffer can be used for storing data prior to it being written to tape. These core technologies give SLR technology the ability to cover a broad range of backup requirements and price points using reliable and cost-effective technology, including the potential in the future to develop SLR drives with native capacities reaching 200GB. Tandberg specifies a 2:1 compression ratio for its SLR tape drives. Native capacities of the SLR100, SLR60 and SLR7 drives are 50GB, 30GB and 20GB respectively. Native data transfer rates are 5 MB/sec, 4 MB/sec and 3 MB/sec respectively. Tandberg also offers an entry-level SLR product line the SLR3, SLR4 and SLR5 which are targeted at low-end workstations. They support native capacities of 1.2GB, 2.5GB and 4GB respectively and native data transfer rates of 380 KB/sec, 300 KB/sec and 300 KB/sec respectively. Minicartridge Drives in this category are based primarily on Imation s Travan technology. Imation Corporation (which was then part of 3M) introduced Travan in 1995 and currently partners with Certance (formerly Seagate Removable Storage Solutions [RSS]) to develop drives based on this technology. Drives based on OnStream Data s Advanced Digital Recording (ADR) technology were previously included in this category. However, after coming back from bankruptcy in May of 2001 as OnStream Data B.V., the company filed for bankruptcy a second time on 28 April 2003. OnStream has not been successful in obtaining new financing, and its operations both in Europe and in the United States have been closed 27 August 2003 3
down. Because this report focuses on drives and technologies that are currently being shipped, ADR is no longer included in the report. Travan Technology Travan technology, which was introduced in December 1994, is based on linear recording technology and is closely related to quarter-inch data cartridge technology. Its design leveraged proven minicartridge technology and maintained backward compatibility with the installed base of drives. It did, however, represent a major advancement in the technology because it was based on a unique drive/cartridge interface developed by 3M. At the heart of the new technology was a different shaped cartridge designed to optimize the amount of tape area for cartridges that can fit in a 3.5-inch form factor tape drive. Data is recorded along the length of the tape with a static read/write head, and drives use single-channel recording and a simple tape path with only two moving parts in the drive. Unique to Travan drives is the track-positioning system with prerecorded servo patterns at both ends of the tape. Through accurate electronic servo signal detection and digital signal processing, the track-positioning algorithm positions the head to the optimal location relative to the data tracks on the tape. When the read/write head is correctly positioned at the beginning of the tape, it is locked into position. A precision tape guidance system built into the Travan data cartridge prevents the tape from wandering. In March 2002 Certance and Imation announced the availability of a new family of sixth-generation Travan drives and media, called Travan 40. This new generation of Travan extended the native storage capacity to 20GB with a native data transfer rate of 2 MB/sec while maintaining backward read compatibility with the 10GB native capacity, 1 MB/sec native data transfer rate Travan 20 (TR-5) drives. Travan drives are specified with a 2:1 compression ratio. To keep drive costs as low as possible, most Travan products use software-based compression, in lieu of compression that is implemented in hardware. The Travan 40 uses Seagate s FastSense technology, which adjusts the speed of the tape drive to match system throughput. FastSense is designed to keep the tape in a streaming mode of operation, helping to optimize backup times. A number of other design enhancements were also added to the Travan 40, including a steel frame for improved durability, a soft-load mechanism to reduce normal wear and tear, and a thermal monitor that activates firmware throttle-down features when drive temperatures reach predetermined levels. A PRML, VR2 data channel was also incorporated to enable higher recording densities, and a park feature that ensures the alignment of recording tracks if a write operation is suspended was added. Certance also continues to ship its previous generation Travan 20 tape drives (based on the TR-5 format) which has a native capacity of 10GB and a native data transfer rate of 1 MB/sec. Drives based on Travan technology are primarily targeted for backup of single-user PCs or workstations and entry-level servers. DLTtape The beginnings of DLTtape date back to 1985 with a half-inch cartridge tape technology that Digital Equipment called CompacTape. CompacTape was a proprietary recording format that recorded data in a serpentine fashion on 0.5-inch-wide tape. The first product of this type from Digital was the 95MB TK50 drive, which was announced in 1985. The major technological advancement for this tape technology came in March 1991 with Digital s introduction of the TF85 line of products, which increased the native capacity to 2.6GB. While still owned by Digital, this technology advanced to 10GB (native) and 1.25 MB/sec (native) and then to 20GB and 1.5 MB/sec (both native). Digital coined the name DLT, which at one time stood for Digital Linear Tape. Quantum acquired the technology from Digital in 1994, when it closed a deal with Digital to buy its magnetic disk drive, tape drive, solid-state disk drive and thin-film recording head operations. Because of the difficulties in trademarking something as generic as Digital 27 August 2003 4
Linear Tape, Quantum later changed the name of the technology to DLTtape, and the DLT in the name is no longer an acronym for digital linear tape. In September 1998, Quantum and Tandberg Data entered into a strategic manufacturing license and marketing agreement that made Tandberg Data an independent second source for DLTtape drives under the Tandberg Data brand name. Tandberg does not, however, have a license to develop drives based on DLTtape technology. In October 2001, Tandberg extended its manufacturing and marketing agreement with Quantum Corporation, with one caveat. This latest agreement allows Tandberg to sell DLTtape and Super DLTtape (SDLT) drives to distributors and original equipment manufacturers (OEMs) that are headquartered in Europe, Asia/Pacific and Japan only, while the U.S. and Latin American markets are left to Quantum. Through the end of 2002, Tandberg manufactured most of the DLTtape drives that it sold. However as part of its actions to reduce operating expenses, Quantum announced plans in September 2002 to outsource its tape drive manufacturing to Jabil Circuit. Beginning in 2003, Tandberg is no longer manufacturing the DLTtape or SDLT tape drives that it is selling under the Tandberg brand. Instead, Tandberg is purchasing the drives that are manufactured by Jabil from Quantum. DLTtape products use a single-reel design whereby the tape cartridge contains the supply reel and the corresponding take-up reel is located in the tape drive. Loading the tape is accomplished by attaching a leader to the end of the tape and using that to pull the tape out of the cartridge, around the tape path, past a stationary read/write head and onto the take-up reel. Today, Quantum sells a DLT 8000 product that scales up to 40GB native and has a native data transfer rate of 6 MB/sec. (Quantum specifies a 2:1 data compression ratio for its DLTtape and SDLT tape drives.) Its two previous models, the DLT 4000 and the DLT 7000, have been discontinued. Quantum also acquired Benchmark Storage Innovations in November 2002, a company that it licensed technology to in 1998 and in which it owned a minority share. In early 1996, Quantum began development of a Valueline series of its DLTtape products. Its intent was to develop lower-cost drives that would enable it to expand the market for its DLTtape technology by moving it into markets in which 4mm Digital Data Storage (DDS) and quarter-inch data cartridge drives were dominant; however, in the following years, Quantum recognized that it had to focus its research and development (R&D) resources on the development of its first-generation SDLT products. As time moved on, it became clear that by the time the Valueline drive could be brought to market, the original design would no longer provide it with the specifications that would allow it to become a competitive force in the market. Therefore, in early 1998 Quantum licensed certain patents and technology to Benchmark (founded in May 1998). Included in the agreement was the transfer to Benchmark of product designs, product hardware and software, and manufacturing tools. In return for the technology license, Quantum retained a 20 percent minority ownership position in Benchmark. The Quantum Valueline technology formed the base for the tape drives that Benchmark would bring to market; however, Benchmark enhanced and built on this technology by incorporating a two-channel magnetoresistive recording head, a soft-unload capability to make it more automationfriendly and a tape path that was different from Quantum s other tape drives. Other enhancements to the original technology included TapeSense circuitry, which is a firmware capability intended to detect whether engagement of the tape leader has properly taken place when a cartridge is inserted into the drive. Benchmark focused on lowering the product cost of its drives through a low parts count and simplicity of design, and the company introduced its first tape drive, called DLT1, in September 1999. In its four-year existence, Benchmark s engineers brought out three tape drive products. Benchmark s first tape drive, the DLT1, was about two-thirds of the height of a full-high, 5.25-inch drive, had a native capacity of 40GB and a native data transfer rate of 3 MB/sec. The company subsequently launched a 27 August 2003 5
half-high version of this drive in April 2001 with the same capacity and data transfer rates as the DLT1. This drive was called the ValuSmart Tape 80, and with its introduction, the company introduced the ValuSmart (VS) name as its new brand. Benchmark s third tape drive, the ValuSmart Tape 160, was announced in June 2002. Still with a half-high form factor, the VS160 doubled the capacity of the previous drive to 80GB native, and the data transfer rate was more than doubled to 8 MB/sec native. The DLT1 drive and VS80 drive use the same DLTtape IV media that is used with the Quantum DLT 4000 and DLT 7000/8000 drives, but in conjunction with the VS160 introduction, Benchmark introduced its own tape media, which it co-developed with Sony. In September 2002, Quantum announced that it had signed a definitive agreement to acquire Benchmark. The deal closed on 13 November 2002, and under the terms of the agreement, Quantum acquired all of Benchmark including its tape drive and tape media products. These are now being integrated with Quantum s DLTtape Group. The Benchmark tape drive products have been integrated into Quantum s DLTtape Group product line. Its autoloader product was integrated into Quantum s Storage Solutions Group (SSG) product line. The ValuSmart Tape 80 and ValuSmart Tape 160 are now called the DLT VS80 and DLT VS160. As part of Quantum s strategy in acquiring Benchmark, these drives will fill out the low-end of Quantum s product line (below SDLT) and become the replacements for the DLT 4000, DLT 7000 and DLT 8000 drives. SDLT The latest incarnation of DLTtape, called Super DLTtape or SDLT, was designed around an entirely new tape architecture, which became the base for future generations of high-end DLTtape products. The nucleus for the SDLT platform is Laser Guided Magnetic-Recording (LGMR) technology. LGMR is Quantum s solution for increasing track densities and recording densities, which in turn equates to higher storage capacities. Several elements, including both optical and magnetic technologies, coalesce to make LGMR what it is and make it the foundation for increasing capacity and performance on future generations of DLTtape. This technology consists of four elements. Magneto-Resistive Cluster (MRC) Heads MRC heads are a group of small magneto-resistive heads that are densely packed together to form a cluster and are held in position using thin-film processing technology. Because the read and write heads are closer together, the clusters are smaller than the heads used on previous DLTtape products. Because the MRC head cannot read the formats written by a DLT 4000, DLT 7000 or DLT 8000 drive, a separate ferrite Metal In Gap (MIG) head and actuator is also incorporated on the drives to provide backward-read compatibility. Pivoting Optical Servo (POS) With POS, SDLT s servo system, Quantum came up with a scheme to utilize the unused side of the media for the servo information. Laser-etched, optically read servo tracks, which are indelible, are placed on the back side of the tape, leaving the other side of the tape free for recording of data. As the tape media moves through the POS, the laser optics follow the servo tracks on the back of the media, tracking the embedded optical targets. The POS assembly pivots around a single mounting point to keep the read/write heads on the recording side of the media aligned with the optical servo tracks when reading from or writing to the tape. This method also allows SDLT media to be magnetically erased without losing the embedded servo tracks. Advanced PRML Jointly developed for SDLT by Quantum and Lucent Technologies, this PRML channel provides a high-level encoding scheme (32/33) which is 97 percent efficient. SDLT Media and Cartridge The SDLT drives use Advanced Metal Powder (AMP) media. It is a multicoated Metal Particle (MP) media, and the back side of the media has a special back-coating that allows the optical servo tracks to be located there. The optical servo is burnished into the media 27 August 2003 6
at the media manufacturer s factory. Quantum believes this gives it a data capacity advantage because the entire front side of the tape remains available for data tracks. The company replaced the leader latching mechanism, previously used on the DLTtape line, with a new design called the Positive Buckle Link. The Positive Buckle Link uses a solid metal pin attached to the drive leader that links with molded clips that are permanently attached to the tape leader inside the cartridge. The metal shield protects the buckling mechanism from striking the head during the load process. When a cartridge is loaded, this pin snaps into the drive leader link. Sensors have been added to prevent missed latching, and firmware changes were made to better control the take-up speed of the tape. The new buckling mechanism also has a mushroom tip on the leader to support and provide backward-compatibility for existing DLTtape IV cartridges. The first SDLT drive, the SDLT 220, has a native capacity of 110GB and a native transfer rate of 11 MB/sec. Quantum specifies a 2:1 data compression ratio for the SDLT drives. Quantum initially came out with a nonbackward read (NBRC) model of the SDLT 220 in the fourth quarter of 2000. A backward readcompatible model began shipping in March 2001, and the NBRC drive was discontinued within months after that due to lack of demand. Quantum s follow-on product to the SDLT 220, the SDLT 320, was released in June 2002, taking SDLT technology to the next level on Quantum s SDLT product road map. It features a native capacity of 160GB and a native transfer rate of 16 MB/sec. The SDLT 320 is backward read and write compatible with the SDLT 220, and it can read the DLTtape IV cartridges written by the older DLTtape, DLT1 and DLT VS80, as well as cartridges used with the DLT VS160 drives. (The SDLT 220 is also backward read compatible with the drives that were developed by Benchmark.). The SDLT 320 uses the same tape media as the SDLT 220 drive. It achieves its higher capacity over the SDLT 220 primarily through an increase in the number of tracks recorded on the tape, which yields a higher recording bit density. The buffer size of the SDLT 320 was also increased to 64MB from 32MB on the SDLT 220. Linear Tape-Open (LTO) Linear Tape-Open (LTO) is an open tape architecture that was developed jointly by three vendors, IBM, Hewlett-Packard and Certance (formerly Seagate RSS). Within the LTO Program, these three are known as the Technology Provider Companies (TPCs). LTO originally consisted of two specifications: Ultrium, which was targeted for capacity-intensive applications, and Accelis, which was designed for accessintensive applications. However, since no manufacturer committed to develop an Accelis-based product, the Accelis format has essentially been shelved. In contrast, the development of drives conforming to the Ultrium specification was pursued by each of the three TPCs. The first-generation LTO Ultrium drives all provide a native capacity of 100GB and a 2:1 data compression ratio. The native transfer rate for the IBM and HP drives is 15 MB/sec, and the native transfer rate of Certance s LTO-1 drive is 16 MB/sec. Data is written on 384 data tracks across the halfinch wide tape. Ultrium uses half-inch-wide MP tape, a multichannel and bidirectional format using a linear serpentine recording method, magneto-resistive (MR) head technology and a magnetic servo. This technology uses a single-reel tape cartridge, with the take-up reel located inside the drive. The tape is engaged via a coupler that grabs a leader pin at the start of the tape and guides it around the tape head to the take-up reel in the drive. After the leader pin is secured in the take-up reel, the reel rotates and pulls the tape through the tape path. The cartridge is similar in shape to Quantum s DLTtape cartridge or an IBM 3480/90 or 3590 cartridge; however, the cartridge is slightly thinner than a DLTtape cartridge. Licenses for the second-generation Ultrium format were made available in April 2002, and the first drive based on Ultrium 2 became generally available from Hewlett-Packard in November 2002. IBM followed with an announcement of its second-generation Ultrium drive on 28 January 2003, though the drive did 27 August 2003 7
not become generally available until 14 February 2003. To date, the third TPC, Certance, has not released its second-generation Ultrium drive. The second-generation Ultrium specification calls for a native capacity of 200GB (using new MP++ media) and a native data transfer rate in the 20 MB/sec to 40 MB/sec range. As with the first-generation LTO drives, the second-generation drives will use a 2:1 data compression ratio. The Generation 2 LTO Ultrium drives still use an eight-channel method of recording. The higher capacity is achieved through the use of the higher coercivity media, an increase in the number of data tracks from 384 to 512 and by implementing a PRML read channel that allows the bit density to be increased by more than 50 percent of the Generation 1 LTO drives. The Generation 2 drives use media that is the same length as the Generation 1 media, but the drives have a faster average tape speed. Generation 2 Ultrium drives can read from and write to a Generation 1 cartridge in Generation 1 format, as well as to Generation 2 cartridges in Generation 2 format. HP s Generation 2 LTO Ultrium drive, the StorageWorks Ultrium 460, has a native capacity of 200GB, like all Ultrium 2 drives. Its native data transfer rate is 30 MB/sec. IBM s second-generation Ultrium drive, the 3580 Ultrium 2, supports up to 200GB of native capacity and a 35 MB/sec native data transfer rate. Other features common to all LTO Ultrium drives are: Recording Format LTO uses a technique called Timing-Based Servo (TBS), in which electronic signals are generated through the real-time reading of servo data bands that are prerecorded on the tape. The signals enable the servo system to dynamically control the positioning of the read/write heads across the width of the tape. The prerecorded servo bands are positioned on the tape parallel to each side of the data bands. Once a data band is filled, the head is aligned on the next prescribed pair of servo bands and begins to write data in that band. The servo bands contain special offsets to ensure that the head is on the correct data band for reading or writing. Reading of a tape occurs in the same way that data are written eight tracks are read simultaneously on each pass down the length of the tape. LTO Cartridge Memory (LTO-CM) All Ultrium tape drives come with LTO Cartridge Memory (LTO- CM), a radio frequency (RF)-based feature that allows certain kinds of data to be stored on a chip rather than in the first region of the tape. As a result, the information is accessible as soon as the cartridge is loaded into the drive rather than when the tape is actually threaded past the read/write head. The types of data that can be stored in LTO-CM include information on the tape contents (such as file location data), information from the tape manufacturer (such as serial number, manufacturer ID number and maximum tape speed) and information from the tape drive manufacturer (such as predictive failure analysis data and information on drive/media health). In all cases, the chip is located in the rear of the Ultrium data or cleaning cartridge where it can be easily read through an RF interface by either a stand-alone drive or possibly in the future by a reader located on the robotics of a tape library. Data in the LTO-CM is protected with parity and Cyclical Redundancy Check (CRC). Interchangeability of Media Because of the open specification, all Ultrium drives support any Ultrium-certified media cartridge regardless of manufacturer. In April 2002, the three TPCs also announced the availability of new universal cleaning cartridges for the Generation 1 and Generation 2 LTO Ultrium drives. The universal cleaning cartridges allow end users to purchase a single cleaning cartridge for use with any first-or second-generation Ultrium drive regardless of the manufacturer. Error Correction Codes (ECCs) The Ultrium format uses ECCs, which are based on two levels of Reed Solomon ECC. The Ultrium ECC is designed to correct most cross-track errors and provide data correction even if a full track is lost. A method of demarcation is used to prevent writing to a bad or defective area of the tape. 27 August 2003 8
Although several of the features of LTO have a base in proven technologies used by other tape formats, the LTO Ultrium format was developed from scratch, with no requirements for backward compatibility. But while the specification is designed to ensure interoperability, it does not mandate such things as drive form factor, drive interface, power consumption, reliability standards, specific data transfer rates, tape speed or specific tape path designs. Each drive/media manufacturer is therefore able to determine how to meet the specification requirements on its own, thus allowing for design ingenuity and competitive differentiation. For more information on LTO Technology, see LTO Tape Technology Overview. Half-Inch Cartridge IBM 3480/3490/3490E Beginning with the early reel-to-reel tape drive, IBM was responsible for several of the half-inch tape technologies that developed into de facto standards within enterprise data centers. Throughout the long life of half-inch reel technology and 3480/3490 technology, IBM s introduction of a new tape format or an enhancement to an existing format was followed 12 to 18 months later by the introduction of drives with the same format by Plug-Compatible Manufacturers (PCMs), such as StorageTek, Hitachi and Fujitsu. Introduced as a successor to the 3420, nine-track half-inch reel drives, IBM s 3480 tape drive revolutionized data center storage in its time with its use of half-inch media contained within a four-inch square cartridge. The change from large tape reels to tape cartridges was the enabling technology that set the stage for the development of modern-day automated backup devices, such as libraries and autoloaders. The 3480 cartridge was used in the early development of tape automation robotics, and its form factor remains the standard for high-end enterprise tape storage today. The first 3480 tape drive was introduced in 1984, with a storage capacity of 200MB using 18-track recording and a 3 MB/sec data transfer rate. Five years later, IBM introduced the 3490 tape drive, adding Improved Data Recording Capability (IDRC) data compaction, which effectively doubled the capacity with no increase in the number of tracks. In February 1991, the track density for 3490 drives was doubled to 36 tracks with the introduction of the 3490E, bringing the native storage capacity to 400MB. A bidirectional recording format, called Enhanced Capability recording, was also introduced for these drives. This was followed in September 1991 by the announcement of support for an enhanced-capacity cartridge a cartridge with a media length of 1,100 feet. The longer-length media doubled the capacity a second time to a native capacity of 800MB; however, these drives were designed to also still support the standard length media. The 3480, 3490 and 3490E all use the same physical size cartridge and each generation provided backward compatibility to prior generations. Several manufacturers also developed lower-cost, smaller form factor versions of 3480/3490/3490E-compatible drives. These drives were typically designed for use in open systems environments and for mounting in a rack cabinet or on a tabletop. IBM 3590B/3590E/3590H In an announcement that was made 11 years after the original announcement of the 18-track 3480 halfinch cartridge technology, IBM announced, in April 1995, a breakthrough in its longitudinal tape recording technology for mainframe drives with the Magstar 3590 Tape Drive. Magstar was designed by IBM to be the long-term market replacement for the 3480/3490/3490E product families. The Magstar 3590 drive was a revolutionary step for mainframe tape, not only because of the increased capacity it offered over 3490E drives, but also because it did not provide for backward-compatibility with cartridges written on 3480/3490 or 3490E drives. With 3480/3490 tape, and with half-inch reel technology before that, mainframe tape was one segment of the market where standards were a bastion and where all formats had to be interchangeable. The tradition of other mainframe tape vendors following IBM s lead by emulating IBM s 27 August 2003 9
technology and introducing compatible products, came to an end with 3590 technology. Most notably, StorageTek decided to take a different technology path and Fujitsu Ltd. was the only other vendor to introduce a 3590 compatible product. Like the 3480/3490 technologies, Magstar technology uses a longitudinal method of recording and halfinch-wide tape, which is housed in a 3490-like cartridge package. The original Magstar also incorporated the same 27-inch tape path as IBM s 3490E tape drive, and the 3490 air bearings and ceramic guides were retained. However, it had major changes from the 3480/3490 technology in the design of the recording head, the electronics and new data compression techniques, all of which enabled significantly higher capacity and performance over 3480/3490/3490E technology. The first Magstar 3590 drives, the B-model drives, incorporated a second-generation 16-track MR head to record data in a longitudinal serpentine method on 128 tracks across the tape. The media for this drive, co-developed by 3M and IBM, was also new, although the cartridge was designed in the same physical size as the 3480/3490/3490E cartridge. This enabled it to be inserted in the same library cartridge slots used for 3480/3490-based libraries. The first Magstar cartridge contained 1,100 feet (320m) of half-inchwide, 1,600-Oe MP media. These drives stored 10GB of uncompressed data on a half-inch cartridge (vs. 800MB on a standard 3490E cartridge), and data were read and recorded at an instantaneous, uncompacted data rate of 9 MB/sec. IBM also changed the data compression techniques on the Magstar drives to Lempel-Ziv (LZ-1) compression (from IDRC data compaction on the 3490 products). Key to this technology was an integrated head assembly that included a track-following servo. The media manufacturer embedded three servo tracks on the media, and the head assembly followed those tracks to ensure accurate alignment. The tape speed is 2 m/sec. Unlike previous IBM half-inch cartridge products, the Magstar 3590 Model B drive was designed with two integrated, separate, fast and wide Small Computer Systems Interface (SCSI) ports on the back of the unit for attachment of the drive to IBM and non-ibm systems. Historically, IBM had different tape products for mainframes and midrange systems, but Magstar was designed and positioned for cross-platform attachment to IBM AS/400 and RS/6000 systems. IBM also targeted sales of its drives to the OEM channel, but OEM shipments of Magstar have not been significant. The Model B Magstar attached to mainframe systems via an ESCON channel connection via the A50 controller, but the SCSI interface allowed the same drive to be used on midrange or smaller systems. IBM continued to enhance the Magstar technology and drives from 1995 through 2000. In 1996, IBM announced a 3590 solution that made Magstar compatible with, and capable of attaching to, StorageTek s silos. In April 1999, new E models of the 3590 were announced that doubled the native capacity from 10GB to 20GB and increased the performance from 9 MB/sec to 14 MB/sec. This increase in capacity was accomplished by doubling the number of data tracks to 256 and using thinner tracks. The tape speed during a read/write operation was increased from 2 m/sec to 3.1 m/sec. The number of recording channels remained at 16, but the recording heads were modified to read the narrower tracks. Other announcements in 1999 included a February announcement of additional open systems support and a July announcement of the A60 controller, which provided twice the performance of the previous A50 controller, as well as support for four ESCON host attachments. In February 2000, IBM further expanded the capacity of its Magstar drives with the introduction of an extended-length data cartridge. The tape in this cartridge has a length of 600m. When used with the E model drives, this double-length tape takes the native capacity from 20GB to 40GB. With this cartridge, the capacity per cartridge was also doubled to 20GB on the B model drives. All B and E models shipped after the date of the announcement were extended-length enabled and capable of using the longer length tape. For a fee, previously installed Magstar drives, whether B or E models, could be upgraded in the field to handle the new tape. Native Fibre Channel attachment for the 3590, E models, was 27 August 2003 10
announced on 20 June 2000 for open systems hosts and storage area networks (SANs). Enhancements to the A60 Control Unit were also announced in October 2000. These A60 enhancements provided native Fibre Channel Connectivity (FICON) support and also allowed for intermixing Enterprise Systems Connection (ESCON) and FICON ports. In June 2002, IBM announced its most recent version of the 3590 tape drive, the 3590H models with general availability on 28 June 2002. With a 14 MB/sec native data transfer rate, the H models are the same as the E model drives in terms of performance. They also have the same drive interfaces (dual SCSI or dual Fibre Channel) as the E models. Like the B and E models, the H model drives attach to ESCON and FICON via the A60 controller (attachment to ESCON via the A50 controller is not available for the H models.). Although there is no increase in the data transfer rate from the Model E drives to the Model H, the 3590 Model H offers up to 50 percent greater capacity due to an increase in the number of data tracks from 256 tracks to 384 tracks. The H model drives incorporate a new head technology to read the narrower tracks. The 3590H models provide a native capacity of 30GB on standard length tape and 60GB with the extended length 3590 cartridge. The H models use the same media that was used on the previous models, and they can also read the 128-track and 256-track formatted cartridges that were written by the 3590 B or E model drives. B or E model drives can be upgraded in the field to the H model. -Fujitsu was the only vendor to develop a Magstar-compatible 3590-tape drive. This drive, called the M8100, was announced in November 1998. It provided compatibility with the IBM B models of the 3590 by recording data on 128 data tracks, but it had a higher native data transfer rate than the B models at 13.5 MB/sec. This drive was only offered with an Ultra SCSI interface, and it has been shipped mainly into the Japanese market. StorageTek 9840/T9840B/T9840C/T9940/9940B The StorageTek 9840 is a high-performance tape drive targeted at applications that require fast data access and disk-like, random-retrieval operations. Although some of the StorageTek TimberLine and RedWood drives had shipped into environments outside of the mainframe arena, the 9840 was the first tape drive developed by StorageTek with the intent of establishing a presence both inside and outside of the glass house with a single product. From the beginning, the 9840 was positioned by StorageTek as a product that can span from NT servers and Unix servers to large MVS mainframe systems. The 9840 cartridge matches the 3480 form factor and can be mixed and matched with 3480/3490 class drives in the same StorageTek tape library. Fundamental to the 9840 s performance is its use of a dual-reel cartridge and self-contained tape path, all incorporated within a 3480/3490-shaped cartridge. By encasing the critical tape guidance, movement and head/tape interface mechanisms within the cartridge, the 9840 eliminates the need to thread the tape onto a second take-up reel within the transport. The drive is ready for operation as soon as the cartridge is loaded into the transport and locked into position. The 9840 cartridge design also contributes to improved reliability, since the tape never leaves the cartridge enclosure, reducing problems that may result from loading and threading the tape and from head/media misalignment. The 9840 automatically loads at the midpoint of the tape, essentially reducing search times and resulting in faster data access speeds during restore operations compared to other tape technologies. Before unloading, the 9840 repositions the tape to its midpoint location for future use. The first-generation 9840 drive is now called the T9840B. In October 2001, StorageTek introduced a second-generation 9840 drive called the T9840B. The T9840B boosts performance over the first-generation 9840, but there was no increase in the drive s capacity. Both the T9840B and T9840A have a native storage capacity of 20GB, and with the use of enhanced LZ-1 data compression technology StorageTek specifies compressed capacities of typically 80GB using a 4:1 compression ratio in MVS/ESCON mainframe environments. In open-system environments running Unix 27 August 2003 11
or Windows NT/2000 on SCSI or Fibre Channel, a 2:1 compression ratio is common, providing compressed capacities up to 40GB. The T9840B supports a native data transfer rate of 19 MB/sec, nearly double that of the original 9840 s 10 MB/sec native data transfer rate. This is primarily the result of a doubling of the tape speed during read/write operations from 2 m/sec (79 ips) on the T9840A to 4 m/sec (158 ips) on the T9840B. Tape speed during rewind and search operations remains the same for both drives at 315 inches/second, and the search speed of the tape is 315 ips, or more than 8 m/sec. The size of the T9840B s data buffer has been increased to 32MB from 8MB on the T9840A. The maximum internal bandwidth of the T9840B was doubled to 70 MB/sec from the 9840 s maximum internal throughput. This allows the Fibre Channel version of the T9840B drive to more fully exploit mainstream 100 MB/sec Fibre Channel connections. The T9840B has also been designed with a 2 Gb/sec Fibre Channel controller interface protecting a customer s investment by providing a growth path into 2 Gb/sec Fibre Channel SAN infrastructures. With 2:1 compression, the T9840B can achieve data transfer rates approaching 40 MB/sec using an Ultra SCSI interface in an open systems environment. StorageTek also claims that performance in ESCON applications was also improved by 20 percent to 50 percent on the ESCON model of the T9840B because the company reduced overhead in the processing channel for ESCON. With this reduction in the protocol overhead, the T9840B supports a sustained data rate of 16 MB/sec over an ESCON channel. On 9 June 2003, StorageTek announced the immediate availability of a native FICON interface for the T9840B drives. StorageTek s implementation of FICON differs from IBM s in that the interface is integrated in the drive in a 1 X 1 architecture. The StorageTek drives connect directly to a FICON Director, whereas IBM uses drives with a native Fibre Channel or SCSI interface which connect to an A60 controller which in turn connects to a FICON Director. Because there was no change in capacity from the T9840A to the T9840B, the data density and number of data tracks did not change from the first to the second generation. Data on both drives is recorded using a thin-film MR head on 288 tracks. In addition to the data tracks, the tape contains five bands of five servo tracks each (25 tracks total) which are prewritten on the tape at the Imation factory. Imation is StorageTek s partner for the media and cartridge for its T9840 and T9940 tape drives and is its exclusive supplier of media/tape cartridges for these drives. On 5 August 2003, a third generation was added to the 9840 family of drives with the introduction of the StorageTek T9840C. On the T9840C, the capacity was doubled over that of the T9840A and T9840B to a native capacity of 40GB. The data transfer rate of the drive was also increased to 30 MB/sec -just over 50 percent higher than the T9840B drive. The key feature of the drives, which is the fast file access time, was carried over to the T9840C. This drive can access any file on the tape in 12 seconds (including the time to load and thread the tape to a ready position). Other features and specifications that are the same on all three generations of the 9840 are a tape motion duty cycle usage time of more than 16 hours a day, support for the same StorageTek libraries and StorageTek s VolSafe, WORM technology. The T9840C is backward-read compatible with cartridges written on the T9840A and T9840B drives, and the cartridges/media that are used with an A or B drive are also the same cartridges that are used for the T9840C. The T9840C was initially introduced with a 2Gb/sec Fibre Channel interface. The availability of an ESCON interface for the drive is planned for December 2003, and a FICON interface is planned for January 2004. The T9940 is StorageTek s capacity centric solution, geared toward environments that require the same class of drive as the T9840, but where the customer prefers greater storage capacity over fast data access times. StorageTek s T9940 tape drive is based on 9840 technology, and essentially the electronics are the same on the two drives. The most distinct differences between the T9840 and the T9940 drives are the data cartridge and the loader mechanism for the cartridge. TheT9940 cartridge is designed with the same form factor and dimensions as the T9840 cartridge, thus enabling it to be used in the same library cartridge slots in the StorageTek libraries. The T9940 cartridge contains a single reel of 27 August 2003 12
media, and the tape path, take-up reel and tape guidance system are located inside the drive. The tape media is the same MP formulation used for the 9840 media, but the length is much longer than the media in a 9840 cartridge. The first-generation T9940A drive has a native capacity of 60GB, and like the 9840, it uses enhanced LZ-1 compression techniques that typically provide 120GB of compressible data in Unix and Windows NT/2000 operating environments and 240GB in MVS mainframe environments. Search time and first access to data averages 41 seconds, or approximately five times that of the 9840 tape drive. The T9940 s average file access time in subsequent searches is 30 seconds, assuming a search of 1/3 the tape length. Tape load and initialize time is 18 seconds, compared with the 9840 s four seconds, and its maximum rewind time is 90 seconds, compared with the 9840 s 16 seconds. Connectivity options for the T9940A support both mainframe and open systems environments using ESCON, Ultra SCSI and Fibre Channel interfaces. In September 2002, StorageTek announced its second-generation T9940 drive, the T9940B, which became generally available in November 2002. The T9940B features a native capacity of 200GB. The higher capacity over the T9940A was primarily achieved by doubling the number of data tracks to 576 tracks and by implementing a PRML encoding scheme. The T9940B uses the Overland Storage VR2 PRML technology. The bit density was increased from 93.7 Kbpi to 157 Kbpi, and there was a slight decrease in the data format overhead. Like the T9940A drive, it reads and writes using a 16-channel recording head. Its data transfer rate is 30 MB/sec native (70 MB/sec compressed), and it has an integrated 2 Gb/sec Fibre Channel interface. An increase in the tape velocity from 2.0 m/sec to 3.4 m/sec contributed to the increased data transfer rate of the 9940B as did the increased bit density and the reduced overhead in the data format. Unlike the first generation drive, the T9940B is not available with a SCSI or ESCON interface because the bandwidth of these interfaces would not be capable of supporting the internal data rate of the drive. The T9940B has the same average file access time (41 seconds), the same tape load and initialize time (18 seconds), and the same maximum rewind time (90 seconds) as the T9940 model (now sometimes referred to as the T9940A). During a search or rewind, the 9940 drives unload the head from the tape to reduce head and media wear. The T9940B is backward read compatible with the T9940A drive, and the same cartridges that are used with the T9940A are used with the T9940B. Helical Scan Technologies Exabyte, Hewlett-Packard and Sony pioneered the use of helical scan technology in small form-factor tape drives for data backup applications. Initially, the plan was to leverage the mechanisms used in video and audio recorders so that the companies would be able to capitalize on economies of scale, thus reducing cost and time to market. This did not happen in the case of DDS products; however, because the consumer audio products never achieved any significant level of market penetration. Helical scan tape drives record data on tracks that are written diagonally on the tape rather than parallel with the tape edge as with linear recording. The read/write heads in helical scan tape drives are mounted on a spinning drum known as a rotary head. The head is oriented at a slight angle relative to the tape. The tape moves in the opposite direction to the spinning rotary head, and multiple tracks are recorded and verified concurrently. Typically, the tape supply and take-up reels are both contained within the cartridge. The exception to this is SAIT technology, which is a single reel technology. In most of these drives, the tape is pulled into the drive and then wrapped partially around the drum. The tape path is therefore part of the device. Helical scan tape drives fall into the following categories based on the type of media or cartridge they use and the width of the tape. 4mm Helical Scan DDS Digital Audio Tape (DAT) was originally developed as a format for consumer audio applications and was later expanded by Hewlett-Packard and Sony in the late 1980s through the DDS standard so that DAT 27 August 2003 13