Quantum 6-00360-15 manual Token Timeouts, Client Configuration

Appendix D Quality of Service Guide

Configuration

Token Timeouts

The RtTokenTimeout parameter controls the amount of time the FSM waits for clients to respond to callbacks. In most normal SANs, the default two- second setting is sufficient. This value may need to be changed for a SAN that has a mixture of client machine types (Linux, NT, IRIX, etc.) that all have different TCP/IP characteristics. Also, large numbers of clients (greater than 32) may also require increasing the parameter.

For example, if the FSM should ever fail, the clients will attempt to reconnect. When the FSM comes back online, the amount of time the clients take to re-establish their TCP/IP connection to the FSM can differ wildly. To avoid unnecessary timeouts, the RtTokenTimeout parameter can be increased, meaning the FSM waits longer for callback responses.

If a client times out on a token retraction, the original requestor receives an error from the FSM that includes the IP address of the offending client. This error is logged to syslog, and alternatively to the desktop on Windows clients. This can help in diagnosing reconnect failures, and in determining if the token time value should be increased.

Client Configuration

When a client obtains a non-real-time I/O token from the FSM, the token allows the client a specific amount of non-real-time I/O. If the client is inactive for a period of time, the token is relinquished and the non-real- time I/O released back to the FSM for distribution to other clients. The timeout period is controlled by the nrtiotokenhold mount option on UNIX platforms, and the QOS Token Hold Time parameter in the mount options tab of the SNFS control panel on Windows platforms. The default is sixty (60) seconds.

This means that after sixty seconds without non-real-time I/O on a stripe group, the non-real-time token for that stripe group is released. The parameter should be specified in five (5) second increments. If it is not, it will be silently rounded up to the next five-second boundary. If the syslog level is set to debug, the file system dumps out its mount parameters so the value can be seen.

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