Re: [sqlite] light weight write barriers
From: Alan Cox
Date: Fri Nov 02 2012 - 08:28:54 EST
> Isn't any type of kernel-side ordering an exercise in futility, since
> a) the kernel has no knowledge of the disk's actual geometry
> b) most drives will internally re-order requests anyway
They will but only as permitted by the commands queued, so you have some
control depending upon the interface capabilities.
> c) cheap drives won't support barriers
Barriers are pretty much universal as you need them for power off !
> Even assuming the drives honored all your requests without lying, how would
> you really want this behavior exposed? From the userland perspective, there
> are very few apps that care. Probably only transactional databases, really.
And file systems internally sometimes. A file system is after all a
transactional database of sorts.
Alan
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