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Chapter 4 Theory
Recording Method
LTO-2 Half-Height Tape Drive User’s Guide 29
Recording Method 4
The LTO-2 Half-Height Tape Drive records data using write-equalized
(1,7) Run Length Limited (RLL) code. RLL (1,7) Data bits are defined as
follows:
•A
ONE is represented by a flux transition at the center of a bit-cell.
•A
ZERO is represented by no flux transition in the bit-cell.
Data Buffer 4
In their default configuration, the LTO-2 Half-Height Tape Drive has a
32-Mbyte buffer. The buffer controller has a burst transfer rate of 320
Mbytes/sec. The high bandwidth is needed to support look-aside data
compression in the case of compressible data being transferred from SCSI
at 160 Mbytes/sec.
Data Integrity 4
The mechanical and electrical design of the drives ensures that drive
performance does not degrade over a drive’s operating life. Changes in
head alignment, head wear, component drift, and other factors are
minimized to ensure that data integrity and interchange capability are
not compromised over the drive's operating life.
The error rate of the LTO-2 Half-Height Tape Drive is less than 1 hard
error in 10
17
bits. The drive’s undetectable error rate is 1 in 10
27
bits read.
Error-correction
Code (ECC)
4
The use of Cyclic Redundancy Checking (CRC), two-level orthogonal
Error Correction Coding (ECC) provides a very low probability of
encountering a hard error. During the read process, ECC correction is
performed on the fly without affecting tape streaming.