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From Sylvain Lebresne <sylv...@yakaz.com>
Subject Re: Quorum: killing 1 out of 3 server kills the cluster (?)
Date Thu, 09 Dec 2010 16:05:37 GMT
I'ts 2 out of the number of replicas, not the number of nodes. At RF=2, you have
2 replicas. And since quorum is also 2 with that replication factor,
you cannot lose
a node, otherwise some query will end up as UnavailableException.

Again, this is not related to the total number of nodes. Even with 200
nodes, if
you use RF=2, you will have some query that fail (altough much less that what
you are probably seeing).

On Thu, Dec 9, 2010 at 5:00 PM, Timo Nentwig <timo.nentwig@toptarif.de> wrote:
>
> On Dec 9, 2010, at 16:50, Daniel Lundin wrote:
>
>> Quorum is really only useful when RF > 2, since the for a quorum to
>> succeed RF/2+1 replicas must be available.
>
> 2/2+1==2 and I killed 1 of 3, so... don't get it.
>
>> This means for RF = 2, consistency levels QUORUM and ALL yield the same result.
>>
>> /d
>>
>> On Thu, Dec 9, 2010 at 4:40 PM, Timo Nentwig <timo.nentwig@toptarif.de> wrote:
>>> Hi!
>>>
>>> I've 3 servers running (0.7rc1) with a replication_factor of 2 and use quorum
for writes. But when I shut down one of them UnavailableExceptions are thrown. Why is that?
Isn't that the sense of quorum and a fault-tolerant DB that it continues with the remaining
2 nodes and redistributes the data to the broken one as soons as its up again?
>>>
>>> What may I be doing wrong?
>>>
>>> thx
>>> tcn
>
>

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