Quantum 3.5 manual Configuration, Non-Realtime Operation, Unit of I/O

Appendix D Quality of Service Guide

Configuration

	Beginning with StorNext release 3.5, QOS has been enhanced to reserve
Non-Realtime Operation
	bandwidth for non-realtime I/O clients. Differentiating between realtime
	and non-realtime I/O clients should result in better bandwidth utilization
	and overall performance.
	During the mounting process, there is now provision to specify the
	amount of bandwidth to be reserved. Applications that do not have
	awareness of the external API can leverage the bandwidth amount. Also,
	clients with different load characteristics can be differentiated.
	Non-realtime I/O support is provided through a central configuration
	file on the FSM server side, which defines the bandwidth reservation for
	non-realtime I/O requests on certain clients. This bandwidth reservation
	(RVIO) has higher priority than normal non-realtime clients, but lower
	priority over the realtime application (RTIO). FSM will always attempt to
	first satisfy realtime requests, and then follow the bandwidth reservation
	request. The remaining bandwidth is even distributed to non-realtime
	clients.
	To summarize, bandwidth priority is allocated in the following order:
	•	Realtime applications (RTIO)
	•	Bandwidth reservation (RVIO)
	• Non-realtime I/O requests
	Note: If there is not sufficient bandwidth to accommodate the
		bandwidth request, the client receives whatever bandwidth
		remains after RTIO requests have been granted.

Configuration

Unit of I/O

The primary configuration for QOS is in the FSM configuration file. No client configuration is required, although there is a QOS tuning parameter that can be specified when the file system is mounted.

Real-time I/O is based on well-formed I/O. This means that for the purposes of determining bandwidth rates, well-formed I/O is

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