nvramdisk: A Transactional Block Device Driver for Non-Volatile RAM

Abstract

In this work, we developed nvramdisk, a transactional block device driver for byte-addressable NVRAM. nvramdisk effectively addresses the key technical challenges in using a section of NVRAM as a transactional persistent block device. nvramdisk adopts (i) shadow block, (ii) mapping table journaling, and (iii) type-dependent ordering guarantee to provide atomicity, consistency, integrity and durability in write operations on nvramdisk imposed block device. We fully implemented nvramdisk device driver on Linux OS and port it on the desktop computer as well as Android smartphones. In memcachedb, locating the database table in nvramdisk brings x 1.9 insertions/sec and updates/sec performance gain against locating the database table in a high-end SSD (FusionIO ioDrive2). SQLite performance increases by x2.9, from 743 ins/sec to 2,184 ins/sec, in smartphone(Samsung Galaxy S4) and x15, from 730 ins/sec to 12390 ins/sec in PC. nvramdisk yields 26 percent higher random write performance against Persistent Memory Block Driver. The overhead of supporting transaction accompanies 6 percent performance penalty in memcachedb operations.