Chapter 4 Theory
Data Compression
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| Data compression algorithms can be tailored to provide maximum |
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| compression for specific types of data. Because varying types of data are |
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| encountered in normal |
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| effective data compression method for a tape drive must serve various |
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| data types. Additionally, the data compression method must adapt to |
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| different data types, automatically providing optimum handling for all |
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| types of data. |
| The tape’s compressed capacity is maximized through the use of | |
| Intelligent Data | |
Compression | intelligent data compression. The intelligent data compression hardware | |
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| determines the compressibility of each record. If the size of the record is |
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| larger after a compression attempt than the native (uncompressed) size, |
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| then the record is written in its native form. |
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| The intelligent data compression utilizes two compression schemes: |
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| • |
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| to achieve data compression. |
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| • |
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| uncompressible data through with minimal expansion. |
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| There are three specific requirements for compliance with the LTO |
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| specification. |
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| • The output data stream must be decompressible following LTO rules |
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| to create the input sequence of records and File Marks perfectly. |
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| • An LTO compressed data stream may not contain any of the eight |
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| reserved Control Symbols. |
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| • While control symbols allow switching to Scheme 2, this should |
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| never be used by operational software because this capability is only |
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| for diagnostic and testing purposes. |
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| Software data compression should never be used because the |
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| |
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| more efficient than software data compression systems. |
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| The |
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| data compression that includes additional control codes for intelligent |
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| data compression. |
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