Quantum 3.5 User Manual

Appendix D  Quality of Service Guide

Callbacks

StorNext 3.5 Installation Guide

158

Figure 62  Non-Real-time 
Token Adjustments

, assume the stripe group is already in real-time mode as a 

result of an 

RTIO

 request from client A. Clients B and D are doing non-

real-time I/O to the stripe group and have a token that specifies the 

amount of non-real-time I/O available. Client C then requests a non-real-

time I/O token in Step 1. The FSM calls back to Clients B and D and 

specifies the new token amount in Steps 2-3. The clients respond in Steps 

4-5, acknowledging the new token amount. The FSM then responds to 

Client C with the new token in Step 6.

4

There are two major failures that affect QOS: FSM crashes and client 

crashes. These can also be loss of communication (network outages). For 

client and server failures, the system attempts to readjust itself to the pre-

failure state without any manual intervention.