HotKey-LSM: A Hotness-Aware LSM-Tree for Big Data Storage

In this paper, to improve the read performance of LSM-tree, we propose an enhanced LSM-tree called HotKey-LSM. The key idea of HotKey-LSM is to put hot keys and cold keys in two separated column families. Thus, when a hot key is not in the block cache, LSM-tree only needs to access a small hot-key LSM-tree to read the key. With this mechanism, most hot-key requests will be answered with low latency: if the hot key is in the block cache, we can return the memory address of the key; if it is not in the cache, we search the small hot-key LSM-tree. This differs from the traditional LSM-tree in that a hot-key request may traverse a large LSM-tree, which causes a high read latency. We implement HotKey-LSM on RocksDB and compare HotKey-LSM with the original RocksDB. The result in terms of QPS suggests the efficiency of our proposal.