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<title>Berkeley DB Reference Guide: Disk drive caches</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Programmer Notes</dl></h3></td>
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<h1 align=center>Disk drive caches</h1>
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<p>Many disk drives contain onboard caches. Some of these drives include
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battery-backup or other functionality that guarantees that all cached
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data will be completely written if the power fails. These drives can
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offer substantial performance improvements over drives without caching
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support. However, some caching drives rely on capacitors or other
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mechanisms that guarantee only that the write of the current sector
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will complete. These drives can endanger your database and potentially
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cause corruption of your data.
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<p>To avoid losing your data, make sure the caching on your disk drives is
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properly configured so the drive will never report that data has been written
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unless the data is guaranteed to be written in the face of a power failure.
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Many times, this means that write-caching on the disk drive must
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