Tandberg Data
Product Specifications
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3-12
Tandberg SLR Reference Manual
3.6.6. Data Error Rate Definitions
The various types of error rates can be divided into
five
different categories:
1)
Hard Write Error Rate
2)
Rewrite Error Rate
3)
Soft Read Error Rate
4)
Raw Read Error Rate
5)
Hard Read Error Rate
Hard Write
Error Rate
This number deals with the situation where the Drive cannot write a block correctly after
performing all recovery operations.
The
Hard Write Error Rate
is expressed in the number of occurrences of this situation;
divided by the total number of bits recorded.
Rewrite
Error Rate
This number deals with the situation where the Drive rewrites a block determined to be bad
during the Read-While-Write control.
The
Rewrite Error Rate
is expressed as the ratio of rewritten blocks vs. the total number of
good blocks recorded. The unit is %.
Soft Read
Error Rate
This number deals with the situation where the Drive must perform a ECC correction or a
read retry operation or both to recover blocks.
The
Soft Read Error Rate
is expressed as the total number of recovery operations
performed divided by the total number of bits read.
NOTE:
The soft error rate counts on block numbers. According to this, the Soft Read Error Rate does not
depend on how many times a single block is re-read.
Raw Read
Error Rate
This number deals with the amount of blocks which cannot be read correctly
without using
ECC
after a complete read/retry sequence has been performed. This number is the actual
input error rate to the ECC system after performing the read retry sequence
.
Hard Read
Error Rate
This number deals with the situation where the Drive fails to read a frame correctly after
passing through the complete read/retry procedure.
The
Hard Read Error Rate
is expressed as the total number of Hard Read Errors divided by
the number of bits read.
NOTE:
A Read error is
not
defined as «hard» until the operator has executed a head-cleaning operation, a
complete retension cycle and a new (failing) Read operation when the Read operation fails on the
same block.