HMSS: A High Performance Host-Managed Shingled Storage System Based on Awareness of SMR on Block Layer

摘要

Shingled Magnetic Recording (SMR) delivers high storage capacity with minimal changes to current production infrastructure. However, it sacrifices random-write capabilities of the devices due to overlaps in the layout of data tracks. This prevents SMR from being widely adapted in practice. In this paper, we present a Host-Managed Shingled Storage (HMSS) system, which supports random writes and provides high performance. HMSS is SMR aware on the block layer and hides the peculiarity of SMR from the upper level. HMSS employs a dynamic address mapping table to ensure that data is written to the sequential-write-required bands through sequential appending. The address mapping table is managed using a very high performance B+ tree and stored in the conventional zone. To reduce the storage overhead of address mapping table, a small amount of conventional zone is used as data cache to aggregate longer contiguous updated LBAs which will be mapped to contiguous PBAs when data is moved from cache to bands. This scheme can not only efficiently make the address mapping table become smaller, but also significantly reduce the number of unavailable space introduced by data update in bands. The performance has been tested and compared with HDD, Flashcache and SSWD. Our measurements implemented in Linux kernel 3.13 show that HMSS provides superb performance. For example, the HMSS is about 62%, 45% and 95% better than HDD, Flashcache and SSWD respectively in random writes.