Half Inch Tape Cartridge Technology

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Half Inch Cartridge
IBM 3480/3490/3490E
IBM is responsible for several of the half-inch tape technologies that have developed into de-facto
standards within enterprise data centers. Introduced as a successor to 9-track, 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 first generation tape reels to tape cartridges was the enabling
technology that set the stage for the development of automated backup devices such as autoloaders and
libraries. The 3480 was the drive used in the early development of tape automation robotics and its form
factor remains the standard for high-end enterprise 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
IDRC hardware compression, which increased storage capacity to 1GB depending on data. The final
generation of 3480 technology, the 3490E, increased the number of recording tracks to 36 and added a
double length tape. The 3490E supports a standard length cartridge with a capacity of 400MB (1.2GB
compressed) and an extended length cartridge with a native capacity of 800MB (2.4GB using data
compression). The 3490E supports a channel data rate of 9 MB/sec. The 3480, 3490 and 3490E all use
the same physical size cartridge and are backward compatible.
IBM 3590B/3590E/3590H
IBM introduced its first generation 3590 tape technology in 1995 in conjunction with media supplier 3M.
The 3590 leveraged many of the 3490E mechanical components while adding the latest advances in
recording technology. The 3590 established a basis for a new extendable tape drive family for use in a
broad range of computing environments.
The latest 3590 drive, the 3590 Model H, was introduced in July 2002 with increases in both capacity and
reliability. The Model H uses a 384-track magnetic recording head versus 256 tracks on the Model E and
128 tracks on the Model B. The 3590 Model E drive can read both 128 and 256 tracks and write 256
tracks to existing cartridges, while the new Model H drive can read both 128 and 256 tracks and write 384
tracks to existing cartridges. The 3590 tape drive uses a bidirectional longitudinal serpentine recording
technique as well as a magneto-resistive head that reads and writes 16 data tracks concurrently.
Using a standard length tape cartridge, the 3590 Model H has a native capacity of 30GB. On the Model E,
it is 20GB and on the Model B it is 10GB. With an extended length cartridge, native capacity doubles to
60GB on the Model H, 40GB on the Model E, and 20GB on the Model B tape drives. The 3590 uses the
IBM LZ1 compression algorithm, which is based on the Lempel-Ziv algorithm and Jackson's class of
encoding methods. The Lempel-Ziv (LZ1) data compression technique provides a compressed capacity
up to 90GB on Model H tape drives, 60GB on Model E tape drives, and 30GB on Model B tape drives
using a standard length tape cartridge (assumes 3:1 compression and compressible data). With an
extended length cartridge, compressed capacity goes up to 180GB on the Model H, 120GB on the Model
E and 60GB on the Model B drives.
The 3590 Models E and H provide a native data transfer rate of up to 14 MB/sec. With Ultra SCSI
attachment, 3590 Models E and H are capable of a maximum instantaneous data rate of 40 MB/sec or
sustained data rates of up to 34 MB/sec (assumes 3:1 compression). With native Fibre Channel
attachment, the maximum instantaneous data rate of Models E and H is 100 MB/sec, with sustained data
rates of up to 42 MB/sec (again assuming 3:1 compression). The 3590 Model B supports a 9 MB/sec

native data transfer rate with a sustained data rate of 34 MB/sec in an Ultra SCSI environment. The Model
B drive does not support a Fibre Channel attachment. All 3590 models support ESCON and FICON
attachment using the 3590 A60 Controller, which enables the drives to be shared between ESCON and
FICON servers. Maximum FICON channel link speed is 100 MB/sec full duplex versus ESCON
performance of 17 MB/sec simplex.
The 3590's Metal Particle (MP) tape media is housed in a cartridge that is physically the same size and
shape as the 3480 cartridge design. They are, however, not compatible in any way. They can be used in
the same automation systems (they are physically compatible in terms of robotics handling), but that is all.
The 3590 cartridge case has been designed so that it can be easily detected by a 3590 drive, but a 3590
drive will reject a 3480, 3490, or 3490E cartridge since they do not have the physical characteristics that
are unique to a 3590 cartridge. The leader block of the 3590 cartridge has also been modified so that any
attempt to mount the cartridge in a 3480, 3490 or 3490E drive will be rejected.
A new MP medium with a much higher coercivity is used in the 3590 cartridge. This is required to support
a high aerial density, and the ability to write a large number of tracks. The 3590 was designed for
increased data integrity and uses Error Correction Code (ECC) and servo tracks that are prerecorded at
the time of manufacture for precise head positioning. These tracks enable the 3590 tape drive to position
the read/write head accurately with respect to the media while the tape is in motion. Additional reliability
features include resident diagnostics that dynamically monitor drive and media performance to detect
potential problems and preemptively aid in resolution. The 3590 also provides redundant data protection
capabilities. By systematically disbursing data across the media as it is written with redundant parity
checking bits, there is a reduced chance of information loss should a media error occur.