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From Mimi Aluminium <mimi.alumin...@gmail.com>
Subject Re: node failure, and automatic decommission (or removetoken)
Date Tue, 01 Mar 2011 09:52:39 GMT
It helps, Thanks a lot,
miriam

On Mon, Feb 28, 2011 at 9:50 PM, Aaron Morton <aaron@thelastpickle.com>wrote:

>  I thought there was more to it.
>
> The steps for move or removing nodes are outlined on the operations page
> wiki as you probably know.
>
> What approach are you considering to rebalancing the token distribution
> when removing a node? E.g. If you have 5 nodes and remove 1 the best long
> term solution is to spread that token range across the remaining 4. This
> will result in additional data streaming.
>
> My understanding is that Cassandra is designed for a relatively stable
> number of nodes in the cluster. With the assumption the failures are
> generally transitory. The features to handle permanent moves and removal are
> somewhat heavy weight and not designed to be used frequently.
>
> Hope that helps
> Aaron
>   On 1/03/2011, at 2:22 AM, Mimi Aluminium <mimi.aluminium@gmail.com>
> wrote:
>
>   Aaron,
> Thanks a lot,
> Actually I meant a larger number of nodes than 3 and replication factor of
> 3.
> We are looking on a system that may shrink due to permanent failures, and
> then automatically detects the failure and stream its range to other nodes
> in the cluster to have again 3 replicas.
> I understnd there is no such script.
> Thanks
> Miriam
>
> On Mon, Feb 28, 2011 at 11:51 AM, aaron morton <aaron@thelastpickle.com>wrote:
>
>>  AFAIK the general assumption is that you will want to repair the node
>> manually, within the GCGraceSeconds period. If this cannot be done then
>> nodetool decomission and removetoken are the recommended approach.
>>
>> In your example though, with 3 nodes and an RF of 3 your cluster can
>> sustain a single node failure and continue to operate at CL Quorum for reads
>> and writes. So there is no immediate need to move data.
>>
>> Does that help?
>>
>> Aaron
>>
>>  On 28 Feb 2011, at 07:41, Mimi Aluminium wrote:
>>
>>  Hi,
>> I have a question about a tool or a wrapper that perform automatic data
>> move upon node failure?
>> Assuming I have  3 nodes with a replication factor of 3. In case of one
>> node failure, does the third replica (that was located before on the failed
>> node ) re-appears on one the of live nodes?
>> I am looking for something that is similar to Hinted Handoff but with with
>> a viable that can be read.
>> I know we can stream manually the data (using nodetool move or
>> decommissions), but is there something automatic?
>> I also found an open ticket 957 but was not sure this is what I am looking
>> for.
>> Thanks
>> Miriam
>>
>>
>>
>>
>>
>>

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