LSM management on computational storage

LSM-trees have emerged as the write-optimized index of choice for key-value stores and relational database systems. LSM-trees typically rely on a storage manager on top of a file system for storing data on Solid-State Drives (SSDs). The I/O path thus comprises four layers, each independently managing similar indirection, journaling, and garbage collection mechanisms. Such overhead is increasingly problematic. First, the advent of microsecond-scale SSDs makes it necessary to streamline the I/O software stack. Second, the increasing performance gap between storage and CPU makes it necessary to reduce CPU storage overhead. A solution is to collapse LSM, file system, and SSD management layers into a single software layer embedded on computational storage. Specific commercial solutions are already available. In this short paper, we describe the design space for LSM management on computational storage.