 As part of their designs, SSDs offer much bigger levels of parallelism for I/O operations, so it is preferable to leave scheduling decisions to their internal logic especially for high-end SSDs.A scalable block layer for high-performance SSD storage, known as "blk-multiqueue" or "blk-mq" and developed primarily by Fusion-io engineers, was merged into the Linux kernel mainline in kernel version 3.13, released on 19 January 2014.This leverages the performance offered by SSDs and NVM Express, by allowing much higher I/O submission rates.