Reducing Read Latency of Shingled Magnetic Recording With Severe Intertrack Interference Using Transparent Lossless Data Compression

Abstract

With the distinct advantage of retaining conventional head and media, the emerging shingled recording technology improves areal storage density through intentional track overlapping that nevertheless introduces severe intertrack interference (ITI). An economically tenable option for shingled drives is to utilize a single read head. As we continue to increase its areal storage density, there will be a higher probability that a read operation demands reading multiple adjacent tracks for explicit ITI compensation. This directly results in a significant read latency penalty when using a single read head. In this work, we propose a simple design strategy to reduce such ITI-induced read latency penalty. If a sector of user data can be compressed to a certain extent, it will leave more storage space for coding redundancy and, hence, opportunistically enable the use of a stronger-than-normal error correction code (ECC). The stronger ECC can accordingly reduce the probability of reading multiple adjacent tracks for explicit ITI compensation. Beyond a simple intrasector compression, the absence of the update-in-place feature in shingled recording makes it feasible to apply lossless compression across multiple consecutive sectors. This can further improve the compression efficiency and, hence, reduce the probability of reading multiple adjacent tracks. We carried out simulations that successfully demonstrate the effectiveness of the proposed design strategies on reducing the read latency penalty caused by severe ITI in shingled recording.