Directions for Shingled-Write and Two-Dimensional Magnetic Recording System Architectures: Synergies with Solid-State Disks (CMU-PDL-09-104)

Shingled-writing and two-dimensional magnetic recording, TDMR, will change core characteristics of magnetic disk operation and require systems software be adapted appropriately. Because a band of adjacent tracks overlap one another, they must be written in a specific order. Once overlapped, a track cannot be updated in place, because the tracks overlapping it will be overwritten by the update. If this behavior is exposed to operating systems directly, there will be very low acceptance of these products. However, disk controller software can emulate full compliance with existing interfaces, and may be able to mask almost all performance implications as well.