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From Edmond Lau <edm...@ooyala.com>
Subject Re: quorum / hinted handoff
Date Fri, 20 Nov 2009 22:25:49 GMT
The key is that an RF of 2 and a cluster size of 3 means that every
piece of data is owned by 2 nodes, and the assignment of data to the 2
nodes responsible for that data is determined by positions in the hash
ring, not by what's up and running.  So if you have nodes A, B, and C,
and a given key hashes to nodes A and B, then taking down either A or
B will prevent a quorum write to those two nodes from succeeding.

Edmond

On Fri, Nov 20, 2009 at 2:14 PM, B. Todd Burruss <bburruss@real.com> wrote:
> not really.  it seems that if i start with 3 nodes, remove 1 of them, i
> should still have a quorum, which is 2.  this is not what i experience.
>
> On Fri, 2009-11-20 at 16:03 -0600, Jonathan Ellis wrote:
>> Oh, okay.  Then it's working as expected.
>>
>> Does it make more sense to you now? :)
>>
>> -Jonathan
>>
>> On Fri, Nov 20, 2009 at 3:43 PM, B. Todd Burruss <bburruss@real.com> wrote:
>> > this was on the build i got yesterday, 882359.
>> >
>> > ... and you are correct about if you start with 2 nodes and take one
>> > down - there isn't a quorum and the write/read fails.  i tested that as
>> > well.
>> >
>> > thx!
>> >
>> >
>> > On Fri, 2009-11-20 at 15:30 -0600, Jonathan Ellis wrote:
>> >> On Fri, Nov 20, 2009 at 11:31 AM, B. Todd Burruss <bburruss@real.com>
wrote:
>> >> > one more point on this .. if i only start a cluster with 2 nodes, and
i
>> >> > use the same config setup (RF=2, etc) .. it works fine.  it's only
when
>> >> > i start with the 3 nodes and remove 1.  in fact, i remove the node
>> >> > before i do any reads or writes at all, completely fresh database.
>> >>
>> >> That sounds like a bug.  If you have 2 nodes, RF of 2, and take one
>> >> node down then quorum anything should always fail.
>> >>
>> >> Is this on trunk still?
>> >>
>> >> -Jonathan
>> >
>> >
>> >
>
>
>

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