On Fri, Jan 14, 2011 at 6:21 PM, Ryan Zezeski <[email protected]> wrote:
> > On Fri, Jan 14, 2011 at 5:46 PM, Mark Phillips <[email protected]> wrote: >> >> >> 2) seancribbs and jiboumans had a quick chat about Read Repair in >> action (via #riak) >> >> * Gist here ---> https://gist.github.com/780363 >> >> * More on Read Repair on the wiki - >> http://wiki.basho.com/Riak-Glossary.html#Read-Repair >> >> > Sean, could you please clarify two points for me. > > 1) Read Repair > > Quote from the wiki -- "Read repair<http://wiki.basho.com/Riak-Glossary.html> > occurs > when a successful read occurs — that is, the quorum was met — but not all > replicas from which the object was requested agreed on the value" > > However, the OP said his get did not work the first time, so wouldn't that > mean the quorum wasn't met and therefore no read repair should have > occurred? That doesn't seem right but that's what I take away from the wiki > definition. > Crap, the second after I hit "send" the lightbulb goes on! Why is that? The quorum _was_ met (all vnodes just migrated to the one machine) but since some of them were fail-overs they didn't have the value yet (or the wrong value)? In this case a read repair happened and subsequent gets worked. I'm still dark on the second question. > 2) Why doesn't r=1 work? > > In the IRC session, you claimed that r=1 would not have helped this > problem. Just like the OP, this confused me. You then went on to say it > was because of some optimization and then mentioned a "basic quorum." > > I took a few minutes to think about this and the only conclusion I came to > is that when r=1 you will treat the first response as the final response, > and in this case the notfound response will always come back first? I'm not > sure if what I just said makes sense but I would have expected r=1 to work, > just like the OP. I'll admit that I still haven't read all the wiki docs > yet (but I've read Read Repair 3 times now), so I'd be happy to hear RTFM. > > -Ryan >
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