Flash-based Extended Cache for Higher Throughput and Faster Recovery

TL;DR

This paper introduces FaCE, a flash-based caching strategy that enhances transaction throughput and recovery speed by using flash memory as an extension to DRAM, with novel algorithms and proven effectiveness in PostgreSQL.

Contribution

FaCE presents new algorithms for flash cache management and demonstrates that small flash caches can outperform larger ones in throughput, improving database recovery and performance.

Findings

Small flash caches can outperform larger ones in throughput.

FaCE reduces disk access and optimizes flash writes.

Effective in PostgreSQL with TPC-C benchmarks.

Abstract

Considering the current price gap between disk and flash memory drives, for applications dealing with large scale data, it will be economically more sensible to use flash memory drives to supplement disk drives rather than to replace them. This paper presents FaCE, which is a new low-overhead caching strategy that uses flash memory as an extension to the DRAM buffer. FaCE aims at improving the transaction throughput as well as shortening the recovery time from a system failure. To achieve the goals, we propose two novel algorithms for flash cache management, namely, Multi-Version FIFO replacement and Group Second Chance. One striking result from FaCE is that using a small flash memory drive as a caching device could deliver even higher throughput than using a large flash memory drive to store the entire database tables. This was possible due to flash write optimization as well as disk access reduction obtained by the FaCE caching methods. In addition, FaCE takes advantage of the non-volatility of flash memory to fully support database recovery by extending the scope of a persistent database to include the data pages stored in the flash cache. We have implemented FaCE in the PostgreSQL open source database server and demonstrated its effectiveness for TPC-C benchmarks.