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Ensuring data reaches disk

Ensuring data reaches disk

Posted Sep 16, 2011 10:35 UTC (Fri) by andresfreund (subscriber, #69562)
In reply to: Ensuring data reaches disk by scheck
Parent article: Ensuring data reaches disk

If the storage device has a write cache but no independent power supply you have the problem that you will loose data on power loss because O_DIRECT will only guarantee that the write reaches the device, not that it reaches persistent storage inside that device.
For that you need to issue some special commands - which e.g. fsync() knows how to do.
Besides an O_DIRECT write doesn't guarantee that metadata updates have reached stable storage.

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