Möbius: A high performance transactional SSD with rich primitives

Abstract

Providing transactional primitives of NAND flash based solid state disks (SSDs) have demonstrated a great potential for high performance transaction processing and relieving software complexity. Similar with software solutions like write-ahead logging (WAL) and shadow paging, transactional SSD has two parts of overhead which include: 1) write overhead under normal condition, and 2) recovery overhead after power failures. Prior transactional SSD designs utilize out-of-band (OOB) area in flash pages to store transaction information to reduce the first part of overhead. However, they are required to scan a large part of or even whole SSD after power failures to abort unfinished transactions. Another limitation of prior approaches is the unicity of transactional primitive they provided. In this paper, we propose a new transactional SSD design named Möbius. Möbius provides different types of transactional primitives to support static and dynamic transactions separately. Möbius flash translation layer (mFTL), which combines normal FTL with transaction processing by storing mapping and transaction information together in a physical flash page as atom inode. By amortizing the cost of transaction processing with FTL persistence, MFTL achieve high performance in normal condition and does not increase write amplification ratio. After power failures, Möbius can leverage atom inode to eliminate unnecessary scanning and recover quickly. We implemented a prototype of Möbius and compare it with other state-of-art transactional SSD designs. Experimental results show that Möbius can at most 67% outperform in transaction throughput (TPS) and 29 times outperform in recovery time while still have similar or even better write amphfication ratio comparing with prior hardware approaches.