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user205537
Asked: 2014-01-15 15:57:06 +0800 CST

Flashcache Power Failure

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iam using ssd for caching other disks ( flashcache module ) if a power failure happened write operations will just stop suddenly and lead to bad sector due to incomplete cache back to devices ( sata disks ) so is there is a way to continue get cache from ssd to devices ( disks ) after server startup, as the cache already stored on ssd?

Many thanks in advance

flashcache

3 Answers

  1. You need to protect your site/facility power first. Please use an appropriately-sized UPS with enough run time.

    Beyond that, I'm an advocate of quality SSDs. You want to use a good SSD with a super-capacitor onboard to protect in-flight data.

    If you're asking about general cache persistence, that's another topic.

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  2. According to the documentation:

    It is important to note that in the first cut, cache writes are
non-atomic, ie, the "Torn Page Problem" exists. In the event of a
power failure or a failed write, part of the block could be written,
resulting in a partial write. We have ideas on how to fix this and
provide atomic cache writes (see the Futures section).

    So it sounds like flashcache can't do what you want.

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  3. Best Answer

    Actually after testing flashcache using write-back cache method i were able to continue getting already stored cache on ssd back to cached disks after power failure or a crash normally using flashcache_load. It looks like the official documentation is outdated.

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