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Appendix D Quality of Service Guide
Callbacks
StorNext 3.1.3 Installation Guide 149
Figure 62 Non-Real-time
Token Adjustments
In Figure 62, 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.
Failure Semantics 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.