An interface device includes a first proxy interface configured to carry out first direct memory access (DMA) transactions initiated by an input/output (I/O) device and a second proxy interface configured to carry out second DMA transactions initiated by a storage drive. A buffer memory is coupled between the first and second proxy interfaces and configured to temporarily hold data transferred in the first and second DMA transactions. Control logic is configured to invoke the second DMA transactions in response to the first DMA transactions so as to cause the data to be transferred via the buffer between the I/O device and the storage drive.