Hardware service time

The hardware service time refers to the time from the START SUBCHANNEL (SSCH) instruction through to the I/O termination interrupt.

In the case of storage systems, the hardware service time varies greatly depending on whether a cache hit or a cache miss is involved.

In the case of inputs/outputs with a block size of 4 KB, a typical value for a cache hit is below 1 ms. In this case the value for a cache miss is up to 10 ms.