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Histogram-based predictions in RAVE

Starting in Data ONTAP 8.2.1, the speculative read-ahead engine (RAVE) in WAFL can capture additional temporal data about previous user read requests to a file and use this information to intelligently speculate on future read requests. In prior releases, speculation was based only on information from the current user I/O.

For clustered systems, you can enable histogram-based predictions as part of the QoS read-ahead settings, and then attach them to a QoS workload. The qos settings read-ahead create | modify read_ahead_setting_name -use-histogram true | false command enables or disables the functionality. The qos workload modify -read-ahead read_ahead_setting_name -workload workload_name command attaches the read-ahead setting to any workload.