> > From our previous discussion of 2-phase commit, there was concern that
> > the failure modes of 2-phase commit were not solvable. However, I think
> > multi-master replication is going to have similar non-solvable failure
> > modes, yet people still want multi-master replication.
>
> No. The real problem with 2PC in my mind is that its failure modes
> occur *after* you have promised commit to one or more parties. In
> multi-master, if you fail you know it before you have told the client
> his data is committed.
Hmm ? The appl cannot take the first phase commit as its commit info. It
needs to wait for the second phase commit. The second phase is only finished
when all coservers have reported back. 2PC is synchronous.
The problems with 2PC are when after second phase commit was sent to all
servers and before all report back one of them becomes unreachable/down ...
(did it receive and do the 2nd commit or not) Such a transaction must stay
open until the coserver is reachable again or an administrator committed/aborted it.
It is multi master replication that usually has an asynchronous mode for
performance, and there the trouble starts.
Andreas
