MRAMFS: A Compressing File System for Byte-Addressable Non-Volatile RAM

Published as Storage Systems Research Center Technical Report UCSC-SSRC-11-02.

Abstract

File systems combining block storage with non-volatile RAM (NVRAM) allow large improvements in file system performance. However, current technology limits low-cost use of NVRAM to relatively low capacities; we examined in-memory compression methods which allow for significantly more efficient utilization of this limited resource. The first phase of the study measured the compressibility of these objects for a set of representative file systems. We found that inodes are compressible by at least 76-90% at a rate of 270–900 thousand inodes per second for the best algorithms. Files in the range of 4-128 KB were compressible of 40–60% at rates of 20–40 megabytes per second. In the second phase of the study, we developed a prototype in-memory file system which utilizes data compression on inodes, and attempted preliminary support for compression of file blocks. This file system, MRAMFS, allowed for the examination of data structures tuned for storage efficiency in non-volatile memory. It showed that for metadata operations, inode compression does not significantly impact performance, while significantly reducing the space used. It also showed that a naive implementation of block-based file compression does not perform acceptably either in terms of speed or compression achieved.

Publication date:
March 2011

Authors:
Nate Edel

Projects:
Storage Class Memories

Available media

Full paper text: PDF

Bibtex entry

@techreport{edel-ssrctr11,
  author       = {Nate Edel},
  title        = {{MRAMFS}: A Compressing File System for Byte-Addressable Non-Volatile {RAM}},
  institution  = {University of California, Santa Cruz},
  number       = {UCSC-SSRC-11-02},
  month        = mar,
  year         = {2011},
}