IBM Magstar MP 3570 C Series, Информация по обслуживанию

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A New Cartridge and Tape Movement Technology
The 3570 introduces a new concept for IBM tape drives that increases reliability along with faster data
access. The 3570 drive, a key component of the 3570 Tape Subsystem, uses a new cartridge with a
supply spool and a take-up spool. The normal start point for the 3570 tape is the physical mid point of the
tape's length. As a result, to access data after the cartridge is loaded and has reached load point, the
maximum distance it must travel is 1/2 the length of the tape, and the average distance is only 1/4 the
length of tape. This reduced travel shortens data retrieval time and reduces head wear. Delays needed
for tape load threading by other tape products is eliminated since the 3570 tape cartridge never needs to
be threaded. When stationed at load point, which is near the center of the tape, the 3570 is ready to read
or write data immediately in either direction.
Interleaved Longitudinal Recording Technology
The 3570 Tape Subsystem reads and writes in a new 128-track format using the serpentine interleaved
longitudinal recording technology, first introduced with the IBM 3590 High Performance Magnetic Tape
Subsystem.
There are two versions of the cartridges, the original B-Format and the newer, C-Format. For C-Format
cartridges, the Magstar MP drives have sustained data rates of 7MB/sec native and 15MB/sec with
maximum compression. For B-Format cartridges, the Magstar MP drives have sustained data rates of
3.5MB/sec native and 10.5MB/sec with 3:1 compression. The drive burst data rate is 20MB/sec. The
average load and initialize time is 8 seconds, and the average search time to first byte of data is 8
seconds.
Writing and reading, with this improved methodology, along with beginning in the center of the tape, allows
high speed data access at a very low cost.
The interleaved longitudinal recording technology allows the 3570 to write multiple tracks from the center
of the physical tape to the end, in either direction, then index the head, or move the head vertically, for the
return trip. The result is tracks interleaved across the width of the tape, from the center out in both
directions.
Using the Magstar MP C-Format cartridges, the Magstar MP 3570 Tape Subsystem drive reads and writes
data on 128 tracks per cartridge, eight tracks at a time. The subsystem uses an interleaved serpentine
longitudinal recording format. The first set of eight tracks is written from the mid-point along the length of
the tape to near the end of the tape, where the head is indexed to the next set of eight tracks for return to
the tape mid-point. This process continues until all 128 tracks are written, and then is repeated for the
other half of the medium until the tape is full. Operation using the Magstar MP B-Format cartridges is
similar to the C-Format cartridge operation, except that four tracks, instead of eight tracks, are written at a
time until all 128 tracks have been written.
Data is written on or read from metal particle tape enclosed in a tape cartridge. The Magstar MP Fast
Access Linear Tape cartridges are different from cartridges used in other IBM tape storage products, and
cannot be interchanged with the media used in other IBM tape products.
Historical Comparison of Tape Technologies
See Figure 17 on page INTRO-5 for an explanation of the historical changes that have led to this new
technology.
Historically, the 18 tracks recorded on 3480 media were used to record ECC information along with the
data. The original base 3490 models also used the same 18-track format but were later enhanced in the
3490E models, which implemented two sets of 18 tracks. In the 3490E device the first 18 tracks are
INTRO-4
IBM 3570 MI