Fault isolation capabilities made available by user space can be provided for a embedded network storage system without sacrificing efficiency. By giving user space processes direct access to specific devices (e.g., network interface cards and storage adapters), processes in a user space can initiate Input/Output requests without issuing system calls (and entering kernel mode). The multiple user spaces processes can initiate requests serviced by a user space device driver by sharing a read-only address space that maps the entire physical memory one-to-one. In addition, a user space process can initiate communication with another user space process by use of transmit and receive queues similar to transmit and receiver queues used by hardware devices. And, a mechanism of ensuring that virtual addresses that work in one address space reference the same physical page in another address space is used.