Tuning Quality of Service Bandwidth Management (QBM)

Beginning with StorNext 6, the Quality of Service Bandwidth Management feature provides a way to spread I/O bandwidth among a number of clients in a controlled and configurable manner.

This feature can be used to manage I/O bandwidth usage by Distributed Data Movers (DDM) by configuring the DDM clients as lower priority than other clients. Other clients are monitored using the client qustats, and the results are reported back to the FSM. The FSM uses that information to throttle DDM activity when clients are active, and to allow greater usage when client activity is low. The non-DDM clients are referred to as non-regulated clients, as there is no throttling of I/O on those clients.

This feature can also be used to manage all clients accessing a file system. Clients that are not configured explicitly are allocated bandwidth using default values. The classes are:

  • First Come: Used to prioritize clients actively using bandwidth above new clients.
  • Fair Share: Used to share I/O bandwidth equally or proportionally between identified clients.
  • Low Share: Used in conjunction with the main classes, First Come and Fair Share.

To configure QBM, you must specify the maximum I/O bandwidth for each stripe group. Tools are supplied to assist with measuring the bandwidth.