In other papers I propose the idea of disk-directed I/O for multiprocessor file systems. Those papers focus on the performance advantages and capabilities of disk-directed I/O, but say little about the application-programmer’s interface or about the interface between the compute processors and I/O processors. In this short note I discuss the requirements for these interfaces, and look at many existing interfaces for parallel file systems. I conclude that many of the existing interfaces could be adapted for use in a disk-directed I/O system.