Decommission doesn't need a RF > 1 since it is run from the node being removed from the cluster. It gives the data to the next node in the ring, that will be responsible for it before leaving.
Removenode (At least if it is like the old removetoken) use replicas to dispatch the data to their new nodes. So yes, this one needs a RF > 1, but has the advantage that it can be used having a node totally unreachable.

But anyway having a RF = 1 is pretty bad since you have a SPOF (Single Point Of Failure) which can be avoided by C* with a higher RF.

Alain


2013/3/19 Marco Matarazzo <marco.matarazzo@hexkeep.com>
Is nodetool removenode / decommission actually needed having a RF > 1 ? What does it do, exactly ?

Il giorno 19/mar/2013, alle ore 16:45, Alain RODRIGUEZ <arodrime@gmail.com> ha scritto:

> In 1.2, you may want to use the nodetool removenode if your server i broken or unreachable, else I guess nodetool decommission remains the good way to remove a node. (http://www.datastax.com/docs/1.2/references/nodetool)
>
> When this node is out, rm -rf /yourpath/cassandra/* on this serveur, change the configuration if needed (not sure about the auto_bootstrap param) and start Cassandra on that node again. It should join the ring as a new node.
>
> Good luck.
>
>
> 2013/3/19 Hiller, Dean <Dean.Hiller@nrel.gov>
> Since you "cleared" out that node, it IS the replacement node.
>
> Dean
>
> From: Jabbar Azam <ajazam@gmail.com<mailto:ajazam@gmail.com>>
> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Date: Tuesday, March 19, 2013 9:29 AM
> To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Subject: Re: Recovering from a faulty cassandra node
>
> Hello Dean.
>
> I'm using vnodes so can't specify a token. In addition I can't follow the replace node docs because I don't have a replacement node.
>
>
> On 19 March 2013 15:25, Hiller, Dean <Dean.Hiller@nrel.gov<mailto:Dean.Hiller@nrel.gov>> wrote:
> I have not done this as of yet but from all that I have read your best option is to follow the replace node documentation which I belive you need to
>
>
>  1.  Have the token be the same BUT add 1 to it so it doesn't think it's the same computer
>  2.  Have the bootstrap option set or something so streaming takes affect.
>
> I would however test that all out in QA to make sure it works and if you have QUOROM reads/writes a good part of that test would be to take node X down after your node Y is back in the cluster to make sure reads/writes are working on the node you fixed…..you just need to make sure node X shares one of the token ranges of node Y AND your writes/reads are in that token range.
>
> Dean
>
> From: Jabbar Azam <ajazam@gmail.com<mailto:ajazam@gmail.com><mailto:ajazam@gmail.com<mailto:ajazam@gmail.com>>>
> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org><mailto:user@cassandra.apache.org<mailto:user@cassandra.apache.org>>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org><mailto:user@cassandra.apache.org<mailto:user@cassandra.apache.org>>>
> Date: Tuesday, March 19, 2013 8:51 AM
> To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org><mailto:user@cassandra.apache.org<mailto:user@cassandra.apache.org>>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org><mailto:user@cassandra.apache.org<mailto:user@cassandra.apache.org>>>
> Subject: Recovering from a faulty cassandra node
>
> Hello,
>
> I am using Cassandra 1.2.2 on a 4 node test cluster with vnodes. I waited for over a week to insert lots of data into the cluster. During the end of the process one of the nodes had a hardware fault.
>
> I have fixed the hardware fault but the filing system on that node is corrupt so I'll have to reinstall the OS and cassandra.
>
> I can think of two ways of reintegrating the host into the cluster
>
> 1) shrink the cluster to three nodes and add the node into the cluster
>
> 2) Add the node into the cluster without shrinking
>
> I'm not sure of the best approach to take and I'm not sure how to achieve each step.
>
> Can anybody help?
>
>
> --
> Thanks
>
>  Jabbar Azam
>
>
>
> --
> Thanks
>
> Jabbar Azam
>

--
Marco Matarazzo
== Hex Keep ==

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