Cosa FS: A Cooperative Shingle-aware File System

The disk drives are approaching the density limit affected by the super-paramagnetic effect. Among the new recording techniques, shingled magnetic recording(SMR) is currently the most attractive one,giving a conservative estimate of density increase about2.3. Although SMR exhibits its merits in expanding the disk capacity, it also suffers from the explicit drawback of random write that rewriting a prior track could not be accomplished without damaging those subsequent tracks. Supporting random out-of-place write/update in shingle-aware file system is a hot topic at home and abroad.In this paper, we design and implement a cooperative shingle-aware file system CosaFS and a hybird shingled write disk Cache-SWD(flash-integrated shingled write disk). CosaFS can leverage the knowledge of the underlying Cache-SWD, separate the metadata/data and take into account the information about hot data identification and migration for the improvement of the overall storage system performance. CosaFS uses T13 Banded Device Command which is provided by Cache-SWD to transmit data and manage Write Pointer of Band. Cooperative garbage collection is completed by host-side CosaFS and device-side Cache-SWD cooperatively. CosaFS is responsible for specifying the garbage collection strategy, and Cache-SWD is responsible for block migration in Band. And host-side CosaFS sends context information of garbage collection to device-side Cache-SWD through T13 Banded Device Command.The experimental test show that CosaFS performs better than Seagate Archive HDD and ShingledFS in metadata access speed, file creation speed and file random access speed. Cooperative garbage collection and hot data identification/migration of Cosafs can improve the ability of data update.