Gus Wirth wrote:
Consider the cache on the hard drive. One of the boasting points of hard drive manufacturers is the size of the RAM cache for the drive. What isn't specified is how that cache behaves under a power loss. Does it try and write itself to the disk? Does it just dump everything? Even if the operating system has done a perfect job in syncing memory to disk, it still hasn't really been written out until the drive itself flushes its own cache. And you have no control over that.
I don't believe that this is true. The FreeBSD guys actually went around and around with the disk manufacturers about this back when they moved from 512byte sectors to 4096byte sectors.
There apparently are commands to bypass write caches as well as tell the truth about sector sizes (both very important in terms of atomicity).
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