[Gluster-users] glusterfs performance issues

[Joe Julian]

This entire thread, regardless of implementation, still seems to support the concept that the client needs to retrieve some sort of information from each replica before answering the request.

That means latency. 

Whit Blauvelt <whit.gluster at transpect.com> wrote:

>On Tue, Jan 08, 2013 at 02:42:49PM +0100, Stephan von Krawczynski
>wrote:
>
>> What an dead-end argument. _Nothing_ will save you in case of a
>split-brain.
>
>So then, to your mind, there's _nothing_ Gluster can do to heal after a
>split brain? Some non-trivial portion of the error scenarios discussed
>in
>this thread result from a momentary or longer split-brain situation.
>I'm
>using "split-brain" in the broad sense of any situation where two sides
>of a
>replicated system are out-of-touch for some period and thus get
>out-of-sync.
>Isn't that exactly what we're discussing, how to heal from that? Sure,
>you
>can have instances of specific files beyond algorithmic treatment. But
>aren't we discussing how to ensure that the largest possible portion of
>the
>set of files amenable to algorithmic treatment are so-handled?
>
>> > That's the thing about complex systems. Trivial solutions are
>usually both
>> > simple and wrong. Some work most of the time, but there are corner
>cases. As
>> > we see with Gluster even complex solutions tend to have corner
>cases; but at
>> > least in complex solutions the corners can be whittled down.
>> 
>> Can they? I'd rather say if it is non-trivial it is broken most of
>the time.
>> Ask btrfs for confirmation.
>
>Pointing out that a complex system can go wrong doesn't invalidate
>complex
>systems as a class. It's well established in ecological science that
>more
>complex natural systems are far more resiliant than simple ones. A
>rich,
>complex local ecosystem has a higher rate of stability and survival
>than a
>simple, poorer one. That's assuming the systems are evolved and have
>niches
>well-fitted with organisms - that the complexity is organic, not just
>random.
>
>Computer software, hardware, and the human culture that supports them
>also
>form complex, evolved ecosystems. Can there be simple solutions that
>help
>optimize such complex systems? Sure. But to look only for simple
>solutions
>is to be like the proverbial drunk looking for his keys under the
>streetlight, even though he heard them drop a half-block away, because
>"The
>light is better here." When people try to apply simple solutions to
>complex,
>evolved ecosystems, the "law of unintended consequences" is more the
>rule
>than the exception. Solutions that appear simple and obvious should
>always
>be suspect. Granted, complex, obscure ones also require scrutiny. It's
>just,
>the simple stuff should never get a pass.
>
>Best,
>Whit
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