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From Jeremy Dunck <jdu...@gmail.com>
Subject Re: Write consistency
Date Thu, 08 Apr 2010 15:29:57 GMT
On Thu, Apr 8, 2010 at 7:16 AM, Gary Dusbabek <gdusbabek@gmail.com> wrote:
> On Thu, Apr 8, 2010 at 02:55, Paul Prescod <paul@ayogo.com> wrote:
>> In this¹ debate, there seemed to be consensus on the following fact:
>>
>> "In Cassandra, say you use N=3, W=3 & R=1. Let’s say you managed to
>> only write to replicas A & B, but not C. In this case Cassandra will
>> return an error to the application saying the write failed- which is
>> acceptable given than W=3. But Cassandra does not cleanup/rollback the
>> writes that happened to A & B."
>>
>
> correct: no rolling back.  Cassandra does go out of its way to make
> sure the cluster is healthy enough to begin the write though.

I think the general answer here is don't use R=1 if you can't tolerate
inconsistency?  Still the point of confusion -- if W=3 and the write
succeeds on 2 nodes but fails the 3rd, the write fails (to the
updating client), but is the data on the two successful nodes still
readable (i.e. reading from what was actually a failed write)?

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