Quantum TC-L53FN-AR Betriebsanweisung PDF herunterladen (Seite 54)

Chapter 4 Theory

Data Integrity

40 LTO-5 Tape Drive User’s Guide

one common symbol between them. The two levels are called C1 and

C2.

C1 ECC

As data is written to memory from the data processing unit, the DMA/

ECC interface generates C1 ECC bytes and writes them to memory.

As data is written to tape, the C1 ECC is checked and an interrupt

generated if there is an error. The C1 ECC read from memory is the ECC

that is written to tape.

When data is read from tape and stored into memory, C1 ECC is checked

and:

• If the C1 ECC is good, the “Valid” bit for the codeword pair is set.

• Otherwise, a pointer to the invalid codeword pair is passed to the

C1 ECC correction engine.

• If the C1 ECC correction engine can correct the error, then the

corrected bytes are written to memory, and the Valid bit is set.

• Otherwise, the Valid bit is left cleared.

As data is read from memory to the data processor for decompression,

the C1 ECC is again checked and an interrupt generated if it is not

correct.

C2 ECC

C2 ECC involves three distinct operations:

Encoding: Generating C2 ECC bytes from data bytes (performed by

ECC coprocessor hardware).

Decoding: Generating ECC syndromes from data and ECC bytes,

testing for all-zeroes (performed by ECC coprocessor hardware).

Correction: Generating corrected data from syndromes.

The correction depends on the number and types of errors involved:

• For one known C1 codeword pair in error in a subdata set (C2

codeword), the operation is performed by the ECC coprocessor

hardware.

1 2 ... 49 50 51 52 53 54 55 56 57 58 59 ... 95 96

Keine Kommentare

Quantum TC-L53FN-AR Betriebsanweisung Seite 54