Quantum 6-00360-15 manual Callback Flow for Initial Rtio Request

Appendix D Quality of Service Guide

Callbacks

Figure 60 Callback Flow for

Initial RTIO Request

In the above diagram, a process on client A requests some amount of RTIO in Step 1. Since this is the first request, the FSM issues callbacks to all connected clients (Steps 2-5) informing them that the stripe group is now in real-time mode. The clients respond to the FSM in Steps 6-9. After all the clients have responded, the FSM responds to the original requesting client in Step 10.

If the timer expires and one or more clients have not responded, the FSM must retract the callbacks. It issues a response to the requesting client with the IP number of the first client that did not respond to the callback. This allows the requesting client to log the error with the IP number so system administrators have a chance of diagnosing the failure. It then sends out callbacks to all the clients to which it first sent the callbacks, retracting them to the original state. In our example, it would set the stripe group back to non-real-time mode.

After sending out the callbacks, the FSM waits for a response using the RtTokenTimeout value as before. If a client again does not respond within the timeout value, the callbacks are retracted and sent out again. This repeats until all clients respond. During this time of token retractions, real-time requests cannot be honored and will only be enqueued.

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