Quantum LTO-2 manual Recording Method, Data Buffer, Data Integrity

Chapter 4 Theory

Recording Method

Recording Method

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

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

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 1017 bits. The drive’s undetectable error rate is 1 in 1027 bits read.

Error-correctionThe use of Cyclic Redundancy Checking (CRC), two-level orthogonal

Code (ECC) 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.

LTO-2 Half-Height Tape Drive User’s Guide 29