Jan, et. al.,

On Jan 26, 2007, at 2:37 AM, Naz Gassiep wrote:
I would be *very* concerned that system time is not a guaranteed monotonic entity. Surely a counter or other internally managed mechanism would be a better solution.

As you should be concerned. Looking on my desk through the last few issues in IEEE Transactions on Parallel and Distributed Systems, I see no time synch stuff for clusters of machines that is actually based on time. Almost all rely on something like a Lamport timestamp or some relaxation thereof. A few are based off a tree based pulse. Using actual times is fraught with problems and is typically inappropriate for cluster synchronization needs.

Furthermore, what would be the ramifications of master and slave system times being out of sync?

I'm much more concerned with the overall approach. The algorithm for replication should be published in theoretic style with a thorough analysis of its assumptions and a proof of correctness based on those assumptions. Databases and replication therein are definitely technologies that aren't "off-the-cuff," and rigorous academic discussion and acceptance before they will get adopted. People generally will not adopt technologies to store mission critical data until they are confident that it will both work as designed and work as implemented -- the second is far less important as the weakness there are simply bugs.

I'm not implying that this rigorous dissection of replication design hasn't happened, but I didn't see it referenced anywhere in this thread. Can you point me to it? I've reviewed many of these papers and would like to better understand what you are aiming at.

Best regards,

Theo Schlossnagle

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