[p2p-hackers] Distributed Snapshots

[Thomas Repantis]

Hi Lei Ni,

Many thanks for your reply.  I think the snapshot of A, B, and C will not 
be consistent, since it is unknown which of the messages exchanged with 
D should be included in it.  

Thomas

On Mon, Aug 01, 2005 at 08:04:46PM +1000, Lei Ni wrote:
> Dear Thomas,
> 
> According to my understanding for the Chandy-Lamport algorithm, you
> are correct.
> 
> If you don't save and restore the state for D that means the state for
> D is simply lost and your snapshot is no longer global snapshot.
> 
> 
> 
> 
> Cheers,
> 
> Lei Ni
> 
> 
> ---------- Forwarded message ----------
> From: Aaron Harwood <aharwood at cs.mu.oz.au>
> Date: Jul 31, 2005 11:11 PM
> Subject: Fwd: [p2p-hackers] Distributed Snapshots
> To: Lei Ni <nilei81 at gmail.com>
> 
> 
> you may want to answer this email.
> --aaron
> 
> Begin forwarded message:
> 
> From: Thomas Repantis <trep at cs.ucr.edu>
> Date: 26 July 2005 4:11:20 AM
> To: p2p-hackers at zgp.org
> Subject: [p2p-hackers] Distributed Snapshots
> Reply-To: "Peer-to-peer development." <p2p-hackers at zgp.org>
> 
>  
> Hi all,
> 
> Can someone verify whether I am correct in my understanding of the following:
> The Chandy-Lamport algorithm [1] can produce a distributed snapshot of a
> system only if *all* nodes are running the algorithm.
> 
> In other words, I am looking for a way to get a global snapshot of a system
> of nodes say A, B, and C.  The caveat is that they might exchange messages
> with node D, which will not run a snapshot algorithm.  I am not interested in
> the state of D, but I need a consistent global snapshot of A, B, and C.
> 
> Am I correct in my understanding that Chandy-Lamport cannot help in this case?
> 
> Is there any other way to get a consistent global snapshot of such a
> distributed system?
> 
> Many thanks!
> Thomas
> 
> [1]
> Distributed Snapshots: Determining Global States of a Distributed System
> K. Mani Chandy, Leslie Lamport
> ACM Transactions on Computer Systems 3, 1 (February, 1985), 63-75.
> http://research.microsoft.com/users/lamport/pubs/chandy.pdf
> 
> 
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> http://www.cs.ucr.edu/~trep
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