[Gluster-devel] Client side AFR race conditions?
Martin Fick
mogulguy at yahoo.com
Thu May 1 22:16:22 UTC 2008
--- Gordan Bobic <gordan at bobich.net> wrote:
> Martin Fick wrote:
> > I am curious, is client side AFR susceptible to
> race
> > conditions on writes? If not, how is this
> mitigated?
> >
> >
> > In other words, what prevents conflicts when
> client A
> > & B both write to the same file? Could A's write
> to
> > subvolume A succeed before B's write to subvolume
> A,
> > and at the same time B's write to subvolume B
> succeed
> > before A's write to subvolume B? If so, isn't
> this
> > somewhat similar to a split brain operation? Is
> there
> > some form a transaction layer using file version
> #s
> > that prevents this?
>
> I would imagine the same thing happens as would
> happen on a local FS.
Well, it can't happen on a local FS. On a local FS
one of the clients would win. While you may not know
which one will win, with the scenario I am describing
they both win but on different subvolumes. This would
leave subvolume A with client B having won and
subvolume B with client A having won. Now depending
on which subvolume I read from I will get a different
answer. With a local FS I can only get one answer.
Does that make sense?
-Martin
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