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From Guy Incognito <dnd1...@gmail.com>
Subject Re: read-repair?
Date Thu, 02 Feb 2012 23:17:35 GMT
sorry to be dense, but which is it?  do i get the old version or the new 
version?  or is it indeterminate?

On 02/02/2012 01:42, Peter Schuller wrote:
>> i have RF=3, my row/column lives on 3 nodes right?  if (for some reason, eg
>> a timed-out write at quorum) node 1 has a 'new' version of the row/column
>> (eg clock = 10), but node 2 and 3 have 'old' versions (clock = 5), when i
>> try to read my row/column at quorum, what do i get back?
> You either get back the new version or the old version, depending on
> whether node 1 was participated in the read. In your scenario, the
> prevoius write at quorum failed (since it only made it to one node),
> so this is not a violation of the contract.
>
> Once node 2 and/or 3 return their response, read repair (if it is
> active) will cause re-read and re-conciliation followed by a row
> mutation being send to the nodes to correct the column.
>
>> do i get the clock 5 version because that is what the quorum agrees on, and
> No; a quorum of node is waited for, and the newest column wins. This
> accomplish the reads-see-write invariant.
>


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