Storage Components
Tape Physical Characteristics
Tape Recording Today
Serpentine Helical Scan
•Data Written along tape •Data written diagonally by
•Fixed Files with ECC
spinning head
•Writes to end, reverses and
•Fixed Files with ECC
writes to beginning •Slow tape speed
•Sometimes multi tracks for •Fast Search
speed
•Popular in consumer markets
•High Speed tape motion
•Sony are major protagonists
•Often no head contact
Linear/Serpentine Recording Helical Scan Recording
In attempts to increase the capacity of tape, the parallel format was
abandoned in order to get more tracks across the width of the media. Two
dominant techniques have appeared, serpentine recording and helical scan.
Serpentine recording will write a track or set of tracks in parallel along the tape
from one end to the other and then write another track or track set back to the
beginning, continuing this until the full width of the tape has been used up.
Helical scan tapes are an evolution from the AV industry and achieve high
capacity by writing data in closely laid stripes diagonally across the tape.
Both of theses technologies use fixed block sizes and CRC or ECC codes to
ensure data integrity.
As we will see, tape is not the ideal medium for data processing and is now
more commonly used in backup and archive solutions.
We will discuss the modern role of tape in a later module.