To make efficient use of the magnetic recording system and to ensure reliable read back of the user data, the bit stream written onto the magnetic medium needs to contain overhead for coding and for synchronization patterns.
We aim at minimizing the total overhead while ensuring proper tape operation and meeting the 10−17 to 10−20 bit error rate requirement of tape recording systems.
Furthermore, about 3% to 5% of the tape cartridge is typically reserved for rewriting data. Data is rewritten on-the-fly if too many errors are detected during the read-while-write verification process.
We are designing a more efficient rewrite scheme such that the written and rewritten rows of any particular sub data set are spaced as far apart as possible to mitigate spatial burst errors on tape. The rewrite scheme needs to be designed such that it is very efficient in terms of reducing the rewrite area.
Increasing the rate of the modulation code and the rate of the ECC code as described above results in decreased code overhead. Additionally, it is desirable to minimize the synchronization overhead by decreasing the relative frequency and the length of inserted synchronization patterns without weakening the robustness of the tape operation.
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IBM Research scientist