"This standard defines a scalable interface for use with memory-mapped storage units and other devices. The term ""storage unit"" can encompass rotating@ non-rotating@ volatile@ and non-volatile storage. Issues of concurrency@ latency@ bandwidth@ extensibility@ and negotiation will be addressed. The interface is intended for use with either a single storage unit or with many coordinated storage units. Purpose This standard provides an efficient physical-layer independent interface architecture for storage units that attach directly to memory access buses. In this interface model@ storage units have an attachment to main memory@ rather than an attachment to an input/output (I/O) channel. This simplifies the storage unit design and supports scheduling of data transfers spanning large numbers of units."