Understanding enabled and disabled read-ahead cache mode for logical devices

Enabled read-ahead cache mode

The controller transfers data from the logical device to its local cache in increments equal to the stripe size. This provides excellent overall performance when workloads are steady and sequential. However, if the workload is random or the system I/O requests are smaller than the stripe size, reading ahead to the end of the stripe might degrade performance.

Disabled read-ahead cache mode

The controller transfers data from the logical device to its local cache in increments equal to the system I/O request size, without reading ahead to the end of the stripe. This provides excellent overall performance when the workload is random or the system I/O requests are smaller than the stripe size.

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