Shingled Magnetic Recording, or SMR, is a technique that increases the storage density in magnetic hard drives. While traditional “perpendicular” recording writes tracks on the hard drive platter directly next to each other, SMR writes tracks partially overlapping previously written ones. This leads to those tracks being much narrower and allowing more data to be stored.
However, this means that tracks that have been overlapped cannot be overwritten, or the track that has overlapped it will be destroyed. Those tracks then have to be rewritten, leading to a slower writing process. On top of this, certain SMR drives require the host (the operating system using them) to know how to handle writing sequentially in order to stop the data on the drive’s overlapping tracks from being destroyed.
This doesn’t make SMR hard drives bad, however. For situations where you most likely will never be overwriting data, such as archiving, it would make more sense to buy SMR drives due to the lower cost per GB. However, for active workloads SMR drives may not be the best choice.
Occasionally, CDR receives in SMR Archive HDDs which have been used in high input-out (IO) server environments. The disks have not been able to cope with the high levels of IO, and it has resulted in the failure of the RAID. Our advice is that you should not use SMR disks in file servers or NAS devices.
For a summary video showing how SMR works please visit the Seagate YouTube channel.
For and a detailed 40 minute video, recorded at a conference on SMR, please see the OpenStack Foundation on YouTube.