Seagate’s latest 1TB platters for 3.5″ have shrunk read/write heads to a point that cannot get anything smaller, therefore has bumped into a physical ‘bottleneck’. Furthermore, the recording tracks are placed as close as physically possible to accommodate the maximum amount of storage space. At this point there’s no way around it, so mechanical hard drive makers like Seagate and WD would have to come up with something completely new.
And that’s where Seagate came up with ‘Shingled Magnetic Recording’ (SMR) which works by reducing the space between the tracks and allows overlapping of tracks as shown below. This also will allow Seagate to increase the areal density to scale without the need to shrink the recording head.
Seagate mentioned the following:
When a user needs to rewrite or update existing information, SMR drives will need to correct not only the requested data, but any data on the following tracks. Since the writer is wider than the trimmed track, all data in surrounding tracks are essentially picked up and as a result will need to be rewritten at a later time (Figure 3). When the data in the following track is rewritten, the SMR drive would need to correct the data in the subsequent track, repeating the process accordingly until the end of the drive.
For this reason, SMR groups tracks into bands, where the shingling process stops (Figure 4). This enables an SMR drive to better manage these rewrites. This also improves the drive’s write performance by grouping tracks into bands that optimize the number of tracks that need to be rewritten.
The architecture of a band within an SMR drive is customized for the application in which the drive will be integrated. Each drive family addresses its specific product needs and uses SMR to deliver the best results by application. Seagate also added that this will not require significant investment in producing the drives, therefore will ensure to keep the drive’s costs as low as possible. Its not clear how Seagate’s new recording type will ensure that the older track will not be overwritten, or damage when the newer track is overlapped, but astonishingly, Seagate made a claim to have shipped 1 Million SMR drives. The question of the product’s performance difference and lifespan when data is overlapped on the tracks also arises.
As of now, this will allow 1.25TB per platter, therefore a possibility of 5TB drives with 4 platters and 25% improvement in areal density on the 1st gen SMR drives. Seagate plans to ship these SMR drives by 2014.
Question also arrives, what does WD plan to do to break this barrier?