Real-Time LSM-Trees for HTAP Workloads Hemant Saxena Lukasz Golab University of Waterloo University of Waterloo
[email protected] [email protected] Stratos Idreos Ihab F. Ilyas Harvard University University of Waterloo
[email protected] [email protected] ABSTRACT We observe that a Log-Structured Merge (LSM) Tree is a natu- Real-time data analytics systems such as SAP HANA, MemSQL, ral fit for a lifecycle-aware storage engine. LSM-Trees are widely and IBM Wildfire employ hybrid data layouts, in which dataare used in key-value stores (e.g., Google’s BigTable and LevelDB, Cas- stored in different formats throughout their lifecycle. Recent data sandra, Facebook’s RocksDB), RDBMSs (e.g., Facebook’s MyRocks, are stored in a row-oriented format to serve OLTP workloads and SQLite4), blockchains (e.g., Hyperledger uses LevelDB), and data support high data rates, while older data are transformed to a stream and time-series databases (e.g., InfluxDB). While Cassandra column-oriented format for OLAP access patterns. We observe that and RocksDB can simulate columnar storage via column families, a Log-Structured Merge (LSM) Tree is a natural fit for a lifecycle- we are not aware of any lifecycle-aware LSM-Trees in which the aware storage engine due to its high write throughput and level- storage layout can change throughout the lifetime of the data. We oriented structure, in which records propagate from one level to fill this gap in our work, by extending the capabilities ofLSM- the next over time. To build a lifecycle-aware storage engine using based systems to efficiently serve real-time analytics and HTAP an LSM-Tree, we make a crucial modification to allow different workloads.