# Understanding write-cache mode for logical drives

When using the write-cache-mode option, you can choose from two available settings.

## Write back

For the write-back setting, the operating system sends data to the controller to write to a storage device. Subsequently, the controller sends a confirmation to the operating system before actually writing the data to the storage device. Doing so increases performance, but also contains an element of risk. For example, if there is a power failure, the data currently in the controller cache is lost. This is no risk when using a controller with a battery-backup cache. The battery preserves the data in the controller cache in the event of a power failure.

Attention:
  1. It is possible to lose data if a power outage occurs while using the write back setting without a battery-backup cache device. If your controller does not have a battery-backup cache installed and enabled, consider carefully whether to enable write back on a logical drive. Depending on how you use the system, write back might be undesirable.
  2. If you do not have a battery-backup cache installed and enabled and you set this feature to write back, wait at least 10 seconds after your last operation before you turn off your system. Failure to follow this practice might result in lost data.

## Write through

For the write-through setting, the operating system sends data to the controller to write to a storage device. Subsequently, the controller writes the data to the storage device; then, sends a confirmation to the operating system. This setting can decrease performance, but contains no risk of losing data.

## More information

- Changing the write-cache mode on a logical drive (action)
- Fine-tuning your system

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