An Active Method to Mitigate the Long Latencies for Host-Aware Shingle Magnetic Recording Drives

Abstract

Shingled Magnetic Recording (SMR) is one of the most promising techniques that satisfy the ever-growing storage volume demands. By overlapping tracks, SMR enormously improves the storage area density, which in turn brings higher storage volumes. However, SMR sacrifices the random write performance for better storage volumes. Current SMR drives propose to remedy this problem by employing an in-drive persistent cache to temporally store incoming writes and migrate them to their disk destinations later on. Unfortunately, cleaning processes for the persistent cache takes up to tens of seconds, and the unpredictable timing of these time-consuming operations chokes normal requests and drastically degrades SMR drive performance. In this paper, we propose to remedy this issue by proactively freeing the persistent cache space so that keeping these lengthy processes transparent with regards to normal requests, therefore reducing the long tails and delivering steady and predictable performance for SMR drive-based storage systems. We prototype our design as a Host-Aware SMR drive aware userspace file system, AM FS, and evaluate it on the real HA-SMR drive with libzbc. Evaluations results show that AM FS reduces the long tails of HA-SMR drives.