1. A computer-implemented method for executing a plurality of computer-executable synchronous input/output (I/O) commands in a multiple virtual storage system, the method comprising: receiving, by a processor, a set of synchronous I/O commands that comprises a plurality of synchronous I/O commands, each received from a respective operating system from a plurality of operating systems; selecting, from the set of synchronous I/O commands, a subset of synchronous I/O commands; allocating a shared resource to the subset of synchronous I/O commands; and executing, concurrently, each synchronous I/O command from the selected subset of synchronous I/O commands.