Memory is slow, Disk is fast bitflux.ai

Jared Hulbert of Bitflux says his DiskArray, a sorted-key data structure that stores 4 KiB extents on eight NVMe drives and keeps only an index in RAM, can outperform an AVL tree at large scales by batching and pipelining disk operations. In his tests, DiskArray handled 670,000 inserts per second at 2 billion keys using 264 MiB of RAM, while the AVL tree needed 144 GiB and managed 320,000 inserts per second; pipelined in-RAM B+tree and NextArray designs were faster, but used much more memory.