SMaRT: An Approach to Shingled Magnetic Recording Translation.

Shingled Magnetic Recording (SMR) is a new technique for increasing areal data density in hard drives. Drive-managed SMR (DM-SMR) drives employ a shingled translation layer to mask internal data management and support block interface to the host software. Two major challenges of designing an efficient shingled translation layer for DM-SMR drives are metadata overhead and garbage collection overhead. In this paper we introduce SMaRT, an approach to Shingled Magnetic Recording Translation which adapts its data management scheme as the drive utilization changes. SMaRT uses a hybrid update strategy which performs in-place update for the qualified tracks and out-of-place updates for the unqualified tracks. Background Garbage Collection (GC) operations and on-demand GC operations are used when the free space becomes too fragmented. SMaRT also has a specially crafted space allocation and track migration scheme that supports automatic cold data progression to minimize GC overhead in the long term. We implement SMaRT and compare it with a regular Hard Disk Drive (HDD) and a simulated Seagate DM-SMR drive. The experiments with several block I/O traces demonstrate that SMaRT performs better than the Seagate drive and even provides comparable performance as regular HDDs when drive space usage is below a certain threshold.