Chapter 4 Theory
Data Compression
• For two or more known C1 codeword pairs in error, the matrix is
|
| computed by firmware and the correction is performed by hardware. |
|
| • For one or more unknown C1 codeword pairs, syndromes are |
|
| generated by hardware, error location is computed by firmware, the |
|
| matrix is computed by firmware and the correction is performed by |
|
| hardware. |
| During a write operation, if the servo system detects an error that may | |
|
| |
Faults | result in adjacent data tracks being | |
|
| aborted. The write operation will not continue until the correct servo |
|
| tracking is |
Data Compression
Typical data streams of text, graphics, software code, or other forms of data contain repeated information of some sort, whether it is at the text level where you can readily recognize regular repetitions of a single word, or at the binary level where the repetitions are in bits or bytes. Although most data is unique and random, the binary level data exhibits patterns of various sizes that repeat with varying degrees of regularity.
Storage efficiency is increased if the redundancies or repetition in the data are removed before the data is recorded to tape. Data compression technology significantly reduces or eliminates redundancies in data before recording the information to tape. This increases the amount of data that can be stored on a finite medium and increases the overall storage efficiency of the system.
With data compression, the redundant information in a data stream is identified and represented by codewords or symbols, which allow the same data to be recorded in a fewer number of bits. These codewords or symbols point back to the original data string, using fewer characters to represent the strings. Because these smaller symbols are substituted for the longer strings of data, more data can be stored in the same physical space.
Some important benefits result from data compression in tape drives:
31 |
