Hard drive density
Hard drives today typically use perpendicular magnetic recording (PMR), a method of laying down data on a platter that creates tracks that are about 75 nanometers wide, which is smaller than a flu virus. Seagate introduced its first PMR drive in 2007. The drive, the Barracuda, held 250GB of data per platter. That grew to 1TB per platter by this year.
While that seems like a lot, Seagate predicts that households currently generating 1TB of data monthly through streaming or creating content, viewing photos, and sharing music will increase that data creation by 20 times over the next two years. So, drive density must grow along with that.
The write portion of a hard drive read/write head — think of a record player needle — is what dictates the width of a track because it needs to be larger to incorporate the technology to record the data. SMR technology overlaps the write portion of tracks, leaving only the read portion exposed for the head to later find.
How SMR offers increased density on platters by overlapping tracks
This is how it works: As new data is written, the drive tracks are trimmed, or shingled. Because the reader element on the drive head is smaller than the writer, all data can still be read off the trimmed over overlapped track without compromising data integrity or reliability.
"The HDD industry is experiencing petabyte shipment growth rates greater than 30% per year while at the same time HDD areal density is improving at a rate less than 20% per year," John Rydning, IDC's research vice president, said in a statement. "Shingled magnetic recording technology is a solution that leverages existing drive architecture to help close the gap in these growth rates while at the same time providing a relatively simple yet economical path to higher capacity HDDs for many applications."
One somewhat obvious problem, Seagate admits, is that SMR works best on a new hard drive where tracks are set down sequentially. On older drives, where old tracks are often overwritten, the writes can overlap previously written data on an adjoining track and unintentionally destroy it.
Because of the write overlap issue, SMR groups tracks into bands, where the shingling process stops. This enables an SMR drive to better manage rewrites. Banding also improves the drive's write performance by grouping tracks into bands that optimize the number of tracks that need to be rewritten.
Sign up for CIO Asia eNewsletters.