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From Mahadev Konar <maha...@yahoo-inc.com>
Subject Re: Failure scenarios and consequences
Date Thu, 09 Dec 2010 20:04:34 GMT
Hi Jeremy,
   Responses in line below:

On 12/9/10 11:53 AM, "Jeremy Hanna" <jeremy.hanna1234@gmail.com> wrote:

I looked around on the wiki and in the user list archives and couldn't find something definitive
about certain failure scenarios.

A partition splits the ensemble where a quorum is on one side of the partition
-- if the leader is on the quorum side of the partition, what happens to reads/writes that
go to the non-quorum side?  I assume writes return errors because it can't get to the leader.
 Reads?

> The reads will also fail on all the quorum nodes until a new quorum is elected.

-- if the leader is on the non-quorum side of the partition, I would assume that the quorum
side of the partition would elect a new leader for those clients on its side of the partition.
 However, is there the possibility for the leader on the non-quorum side to accept writes
before it realizes that there's no longer a quorum?  Just wondering about the possibility
of corruption and then when the cluster syncs back up how the cluster would handle that data.

> No there isnt. The leader relinquishes its right as a leader as soon as it realizes a
quorum isnt committing the changes it proposed.

(I would be happy to create a wiki page for failure scenarios if one doesn't exist that people
could add to, but maybe this is just common knowledge.)

> Please do!

thanks
mahadev

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