A first storage system is configured as a proxy for a logical volume stored on a second storage system. The first computer system receives an I/O request from a host computer for the logical volume, the host computer, and identifies a port on the second storage system for the I/O request. In some embodiments, the second storage system has multiple SCSI ports, and the identified port comprises a least busy SCSI port. A probe request verifying availability of the logical volume is conveyed to the identified port, and upon receiving a response from the second storage system verifying the availability of the logical volume for the I/O request, the I/O request is conveyed to the identified port, a result of the I/O request is received from the identified port, the result is conveyed to the host computer.