Quantum LTO-2 User Manual

Chapter 4  Theory

Data Compression

LTO-2 Half-Height Tape Drive User’s Guide

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• 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.

4

During a write operation, if the servo system detects an error that may 

result in adjacent data tracks being over-written, the write operation is 

aborted. The write operation will not continue until the correct servo 

tracking is re-established.

Data Compression

4

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: