MIT Incremental Propagation

[Jeffrey Altman]

John Hascall wrote:
>>> Ubik is an elected-master protocol.  All updates go to the master
>>> which replicates.  If the master goes away, after a while the
>>> remaining nodes notice and revote a new master (this can take a while).
>>>
>>> I'm not sure that model works well with the KDC's single-threadedness.
>>>
>>> I expect a 3-phase commit model would be more robust.
>> I think you're conflating the master election protocol with the
>> transaction protocol.  You still need to decide on a master (aka
>> "coordinator") with 2PC or 3PC.
>
>    You do not.  Each transaction can be mastered by whichever
>    node it starts out on.  As soon as it has >50% acks to the
>    prepare, it can issue the commits.  At the same time another
>    node can be mastering a different transaction.
>
> John
Ken is describing a dynamically selected single master model whereas
John is describing a multiple master model.  They are simply different
models.  Ubik provides for an elected single master and does not support
multiple masters.

Jeffrey Altman

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