Magnetic Tape Partial Data Writing Without Interleaving
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Solution Overview
Problem
When data being written to magnetic tape is smaller than a full Data Set, existing technologies suffer from reduced performance and effectiveness of error correction codes (ECC) due to the need for full Data Set allocation and interleaving, which reduces the spacing of codeword quads and increases latency.
Innovation Solution
A method is introduced to write data in a non-interleaved manner by issuing a do-not-interleave command, computing ECC, and forming codeword sets, which allows for writing at least one codeword set to the tape without interleaving, along with a Data Set Information Table, and optionally writing multiple instances of codeword sets to maintain ECC capability and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a full Data Set is allocated for writing data to magnetic tape, then the data storage structure is maintained, but performance is adversely affected when the data size is smaller than a full Data Set
Solution Approach 1:
The patent segments the traditional fixed-size Data Set into variable-size Sub Data Sets. Each Sub Data Set contains only the necessary data plus ECC codewords, allowing partial Data Sets to be written without allocating full Data Set space. This segmentation enables efficient storage of small data while maintaining the required storage structure.
2Productivity
If fewer codeword quads are written than a full Data Set, then storage efficiency is improved, but interleaving is precluded and ECC error correction capability is reduced
Solution Approach 1:
The patent applies preliminary action by pre-computing both C1 and C2 ECC codes for each Sub Data Set before writing to tape. This advance computation ensures that sufficient error correction capability is built into each Sub Data Set independently, so that even when fewer codeword quads are written (improving storage efficiency), the ECC reliability is maintained through proactive error correction preparation.
3Speed
If non-interleaved writing is used for partial Data Sets, then writing speed is improved, but the spacing of codeword quads is reduced
Solution Approach 1:
The patent segments the data into Sub Data Sets that are written sequentially in a non-interleaved manner. This segmentation allows each Sub Data Set to be written contiguously without the overhead of interleaving operations, improving writing speed. The segment structure naturally accommodates variable spacing requirements while maintaining efficient sequential write operations.
Data Source
AI summary
Methods, logic, apparatus and computer program product write data, comprising less than a full Data Set, to magnetic tape. Data is received from a host, a do-not-interleave command is issued and C1 and C2 ECC are computed. Codeword Quad (CQ) sets are then formed. At least one CQ set of the Data Set is written to a magnetic tape in a non-interleaved manner and a Data Set Information Table (DSIT) is written to the magnetic tape immediately following the at least one written CQ set. An address transformation may be used to cancel interleaving. Writing a CQ set may include writing a plurality of contiguous instances of the CQ set to the magnetic tape to maintain the effectiveness of ECC capability.