Tape ECC Interleaving for Non-Power-of-Two Multi-Track Recording
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Solution Overview
Problem
Current Linear Tape Open (LTO) formats, Generations 3 and 4, are unable to accommodate future tape-drive systems with multiple of eight transducers/sensors per head to read/write multiple of eight concurrent tracks due to limitations in their error-correcting code (ECC) and interleaving schemes.
Innovation Solution
The development of higher-rate and longer C2 codes with a code rate greater than the LTO-3/4 C2 code rate and codeword length, specifically a C2 code with a rate of 84/96 and codeword length of 96, which includes a Reed-Solomon (RS) code, is implemented to enable efficient data recording on multiple tracks while maintaining error rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If current LTO formats use C2 coding scheme with length 64 and rate 54/64, then error correction is provided for up to 16 tracks, but the system cannot accommodate future tape drives with 24, 32, or 48 transducers/sensors per head
Solution Approach 1:
The patent implements a dynamic interleaving scheme where codeword objects are distributed across multiple tracks based on the actual number of active transducers. The system can adaptively configure the interleaving pattern to match any multiple of eight tracks (16, 24, 32, 48), allowing the same C2 code to serve different hardware configurations without requiring separate coding schemes for each track count.
Solution Approach 2:
The patent creates a universal C2 coding framework that functions across multiple track configurations. By using a longer code length of 96 while maintaining the 84/96 rate, the system provides a single ECC solution that universally supports any multiple of eight tracks, eliminating the need for multiple specialized coding schemes.
2Productivity
If C2 code length is increased from 64 to 96 with rate 84/96, then higher data recording rates and better error correction are achieved, but code complexity increases
Solution Approach 1:
The patent changes the fundamental parameters of the C2 code from length 64/rate 54/64 to length 96/rate 84/96. This parameter change increases the code rate (improving productivity by about 55%) and provides better error correction capability, while the underlying Reed-Solomon coding structure remains familiar to implementers.
Solution Approach 2:
The patent segments the data into codeword objects that are then interleaved across multiple tracks. This segmentation approach allows the longer C2 code to be processed in manageable units, reducing the practical complexity of implementation while maintaining the benefits of the longer code length.
3Productivity
If more tracks are written simultaneously (24, 32, 48 tracks), then throughput increases, but error correction capability must be maintained across more tracks
Solution Approach 1:
The patent extends the error correction from a single-track dimension to a multi-track dimension through interleaving. By distributing codeword objects across multiple tracks and using the longer C2 code, the system can correct errors that affect multiple tracks simultaneously (stripe errors), providing reliability that scales with the number of tracks while maintaining high throughput.
Data Source
AI summary
Conventional C2 coding and interleaving for multi-track data tape in LTO-3/4 do not support recording data onto a number of concurrent tracks which is not a power of two. Higher-rate longer C2 codes, which do not degrade error rate performance, are provided. An adjustable format and interleaving scheme accommodates future tape drives in which the number of concurrent tracks is not necessarily a power of two. A data set is segmented into a plurality of unencoded subdata sets and parity bytes are generated for each row and column. The parameters of the C2 code include N2 as the least common multiple of the number of possible tracks to which codeword objects are to be written. COs are formed from N2 C1 codewords, mapped onto a logical data track according to information within headers of the CO and modulation encoded into synchronized COs which are written to the tape.