GCC: Optimizing Space Efficiency and Read Latency of SSDs with Workload-Aware Garbage Collection Aided Compression

Data compression is increasingly employed to enhance throughput and space efficiency in flash-based storage systems, which are critical for data-intensive applications. Current intra-SSD compression techniques operate transparently with respect to the file system and contribute to improving the lifetime of SSDs. These approaches typically avoid compressing read-hot data to reduce the latency penalties associated with decompression. However, the read-hot data remain uncompressed even after turning into cold data, thereby reducing overall compression effectiveness and diminishing space efficiency. Moreover, when previously compressed cold data become read-hot, it necessitates frequent decompression, which increases the read latency. To address the above problems, we propose a novel Garbage Collection aided Compression (GCC) scheme, to optimize space efficiency and mitigate read latency for compression-supported SSDs. The key idea of GCC is exploiting the valid page migration during garbage collection to enable background compression and decompression. Throughout the garbage collection process, the migrated valid pages can potentially be compressed or decompressed, which progressively improves space efficiency and minimizes the need for decompression during read operations. Performance evaluations conducted using MQSim simulator demonstrate that, compared to the typical compression schemes, GCC reduces the read and write latency by 25.27% and 9.43% on average and improves the space efficiency by 15.01% on average.