Among all I/O scheduler types, the noop scheduler is the simplest. While it still implements request merging, it moves all requests into a simple unordered queue, where they are processed by the disk in a simple FIFO order. The noop scheduler has no tunable options

The noop scheduler is suitable for devices where there are no performance penalties for seeks. Examples of such devices are ones that use flash memory. noop can also be suitable on some system setups where I/O performance is optimized at the block device level, with either an intelligent host bus adapter, or a controller attached externally.