Re: POSIX shared memory redux

* Tom Lane:

> Well, the fundamental point is that "ignoring NFS" is not the real
> world. We can't tell people not to put data directories on NFS,
> and even if we did tell them not to, they'd still do it. And NFS
> locking is not trustworthy, because the remote lock daemon can crash
> and restart (forgetting everything it ever knew) while your own machine
> and the postmaster remain blissfully awake.

Is this still the case with NFSv4? Does the local daemon still keep
the lock state?

> None of this is to say that an fcntl lock might not be a useful addition
> to what we do already. It is to say that fcntl can't just replace what
> we do already, because there are real-world failure cases that the
> current solution handles and fcntl alone wouldn't.

If it requires NFS misbehavior (possibly in an older version), and you
have to start postmasters on separate nodes (which you normally
wouldn't do), doesn't this make it increasingly unlikely that it's
going to be triggered in the wild?

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Florian Weimer <fweimer(at)bfk(dot)de>
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