Using high speed data transfer protocol

Using high speed data transfer protocol to transfer data between a host and a storage system includes determining if a portion of data is a candidate for being transferred using the high speed data transfer protocol if the portion is not a candidate for high speed data transfer, transferring the data using a relatively low speed data transfer protocol if the portion is a candidate for high speed data transfer, attempting to transfer the data using the high speed data transfer protocol, and if transferring the data using the high speed data transfer protocol is unsuccessful, transferring the data using the relatively low speed data transfer protocol. The high speed data transfer protocol may use a first connection and the relatively low speed data transfer protocol may use a second connection. The first connection may be a PCIe or InfiniBand connection. The second connection may be a FICON connection.