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Berkeley DB Reference Guide:
  Programmer Notes

### Disk drive caches

Many disk drives contain onboard caches. Some of these drives include battery-backup or other functionality that guarantees that all cached data will be completely written if the power fails. These drives can offer substantial performance improvements over drives without caching support. However, some caching drives rely on capacitors or other mechanisms that guarantee only that the write of the current sector will complete. These drives can endanger your database and potentially cause corruption of your data.

To avoid losing your data, make sure the caching on your disk drives is properly configured so the drive will never report that data has been written unless the data is guaranteed to be written in the face of a power failure. Many times, this means that write-caching on the disk drive must be disabled.

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