SMR - Shingled Magnetic Recording

- Sebastian Evers

The word "shingle" refers to the roof shingles or their arrangement by roofers on a roof. Shingled Magnetic Recording ("layered magnetic recording") refers to a data storage technology to increase the storage density on mechanical hard drives (HDD) and to increase the total capacity of a single hard drive by up to 25%.

In the original storage method, with traditional ferromagnetic data carriers, all of the concentric tracks for storage were written as closely as possible next to one another - separated by a safety distance ("guard space"). With Schingled Magnetic Recording, the writing process takes place so that part of the adjacent memory area always overlaps the previous one; similar to the eponymous shingles on a roof. Through this process, the adjacent track becomes thinner, which means that the density of the individual tracks can be increased significantly.

However, the concept also resulted in the risk of data loss, since the adjacent track is also overwritten with every write operation. In order to counteract this, the adjacent memory area would have to be read out, temporarily stored and also rewritten after the write process. However, since this would apply to all further adjacent tracks and would have to be followed by an entire chain reaction of write operations with each individual write operation, this would slow down regular write operations considerably.

The manufacturer Seagate counteracted this problem by tapes forming a combination of several tracks. The last track of a tape is therefore not overlapped by the first track of the next tape and is therefore not overwritten. This limits the chain reaction of rewriting the overlapping tracks and minimizes the writing effort and the time required to complete the writing.