A storage system interface (SSI) located externally to a data storage system serves as an interface between a host system and the data storage system. The SSI may be part of the host system, and in some embodiments may be a separate and discrete component from the remainder of the host system, physically connected to the remainder of the host system by one or more buses that connect periphery devices to the remainder of the host system. The SSI may be physically connected directly to the internal fabric of the data storage system, and may be implemented on a card or chipset physically connected to the remainder of a host system by a PCIe bus. The SSI may provide functionality traditionally provided on data storage systems, enabling at least some I/O processing to be offloaded from data storage systems to hosts that include SSIs.