[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Vrs-development] IBM Token Ring Thingy...

From: Eric Altendorf
Subject: Re: [Vrs-development] IBM Token Ring Thingy...
Date: Fri, 3 May 2002 10:31:43 -0700

On Friday 03 May 2002 07:20, Chris Smith wrote:
> Yep, but you've still got the problem of two or more LDS's broadcasting the
> 'claim cluster image' to the cluster.  You can't have more than one
> claiming the cluster image, so this should fail.  However, it's really
> difficult to engineer because you've got to detect that all nodes in the
> cluster accepted the SAME claim message from the same LDS.  This is hard
> enough, without the added complication that you may not know about all
> LDS's in the cluster.
> This is why the MA approach may help.  Each LDS maintains it's own view of
> the cluster image, and is kept in sync as best as possible.  It doesn't
> have to be immediate (and I think we should design with this in mind)
> because we have to deal with the case of LDS's going offline and coming
> back.  Thus the MA idea allows all scenarios to be dealt with.  If an LDS
> comes back on line, then a lot might have changed, and the MA 'data tree'
> will return a wealth of information.

OK, I'm starting to see the picture here with the MA.

I think what it boils down to is that if we have no requirement for the 
cluster images to remain consistent among machines, then there are a number 
of different mechanisms we could use.

If we want to guarantee that the CI remains consistent, or remains "at most X 
minutes out of date" or anything else, I think we're going to have to resort 
to transactions.  Pretty much ANY time we want to make a guarantee about data 
consistency across a distributed network, we're going to have to use 
distributed transactions with two phase commit.

By the way -- I would strongly recommend that anyone working on this project 
go to a library and read *Transaction Processing: Concepts and Techniques" by 
Jim Gray and Andreas Reuter.  There are other books, but that's pretty much 
the bible, AFAIK.


"First they ignore you.  Then they laugh at you.
 Then they fight you.  And then you win."             -Gandhi

reply via email to

[Prev in Thread] Current Thread [Next in Thread]