[Drbd-dev] How Locking in GFS works...

Philipp Reisner philipp.reisner at linbit.com
Mon Oct 4 16:09:23 CEST 2004

On Monday 04 October 2004 15:49, Lars Marowsky-Bree wrote:
> On 2004-10-04T15:26:15, Philipp Reisner <philipp.reisner at linbit.com> wrote:
> > If everything works (esp. the locking of the shared disk fs) no.
> >
> > But just consider that the locking of the shared disk FS on
> > top of us is broken, and that it issues a write request to
> > the same block number on both nodes.
> >
> > Then each node would write its copy first and the peers
> > version of the data at second to that block number.
> >
> > => We would have different data in this block on our
> >    two copies. - And we would event know about it!
> You would know the moment the replicated write from the remote end came
> in, no?
> "Oh my, this is dirty locally too and unacked. We better arbitate now;
> ie one side wins and the other one is silently discarded."

This is what I like about mailinglists. This is a new idea, that
certainly needs to be considered. 

Hmm, I just tooks a sheet of paper and drew a view diagrams of it.

It works as long as writing the block takes longer than transmitting
the block.

The scheme simply fails if transmitting takes longer than writing.

: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
: Schönbrunnerstr 244, 1120 Vienna, Austria    http://www.linbit.com :

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