MRAMFS: A compressing file system for non-volatile

File systems using non-volatile RAM (NVRAM) promise great improvements in file system performance over con-ventional disk storage. However, current technology allows for a relatively small amount of NVRAM, limiting the effec-tiveness of such an approach. We have developed a proto-type in-memory file system which utilizes data compression on inodes, and which has preliminary support for compres-sion of file blocks. Our file system, mramfs, is also based on data structures tuned for storage efficiency in non-volatile memory. This prototype will allow us to examine how to more efficiently use this limited resource. Simulations have shown that inodes can be reduced to 15–20 bytes each at a rate of 250,000 or more inodes per second. This is a space savings of 79–85 % over conventional 128-byte inodes. Our prototype file system shows that for metadata operations, in-ode compression does not significantly impact performance, while significantly reducing the space used by inodes. We also note that a naive block-based implementation of file compression does not perform acceptably either in terms of speed or compression achieved. 1