Storage vendors, including but reportedly not limited to Western Digital, have quietly begun shipping SMR (Shingled Magnetic Recording) disks in place of earlier CMR (Conventional Magnetic Recording) disks.

SMR is a technology which allows vendors to eke out higher storage densities, netting more TB capacity on the same number of platters—or fewer platters, for the same amount of TB.

Until recently, the technology has only been seen in very large disks, which were typically clearly marked as “archival”. In addition to higher capacities, SMR is associated with much lower random I/O performance than CMR disks offer.