[Gluster-devel] Client side AFR race conditions?

[Martin Fick]

--- 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



      ____________________________________________________________________________________
Be a better friend, newshound, and 
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ