# Understanding enabled and disabled read-ahead cache mode for logical drives

Note: You can enable and disable the read-ahead setting without destroying data in a logical drive by using the ServeRAID Manager in startable-CD mode.

## Enabled read-ahead cache mode

The ServeRAID controller transfers data from the logical drive to its local cache in increments equal to the stripe-unit 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-unit size, reading ahead to the end of the stripe might degrade performance.

## Disabled read-ahead cache mode

The ServeRAID controller transfers data from the logical drive 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-unit size.

## More information

- Enabling and disabling read-ahead cache mode (action)
- Changing the stripe-unit size (action)
- Understanding stripe-unit size

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