Shingled Magnetic Recording

Overview

Shingled Magnetic Recording (SMR) is an HDD recording technology that writes data sequentially in overlapping ("shingled") regions, grouped into zones. This zone structure is what enables data-safe drive regeneration: when a head fails, only the zones under that head go offline while all other zones remain accessible, avoiding the full reformat that conventional drives require. Host Managed SMR supports a data-safe zoned regeneration flow in which the host backs up the content of the target zones, then issues Remove Element and Modify Zones; existing data in the remaining online zones is unaffected and no format is required. SMR zone sizes are typically 256 MB — the candidate standard zone size for a proposed "CMR Zones" feature that would bring similar depopulation capability to conventional drives. While the very large data center operators are in the process of moving to SMR, many data center providers remain all-CMR and want conventional-drive longevity without undertaking the storage-architecture transition.