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From Zhong Li <...@voxeo.com>
Subject Re: Understanding Virtual Nodes on Cassandra 1.2
Date Wed, 30 Jan 2013 19:43:32 GMT
Are there tickets/documents explain how data be replicated on Virtual Nodes? If there are multiple
tokens on one physical host, may a chance two or more tokens chosen by replication strategy
located on same host? If move/remove/add a token   
manually, does Cassandra Engine validate the case?

Thanks.


On Jan 30, 2013, at 12:46 PM, Zhong Li wrote:

>> You add a physical node and that in turn adds num_token tokens to the ring.
> 
> No, I am talking about Virtual Nodes with order preserving partitioner. For an existing
host with multiple tokens setting list on cassandra.inital_token. After initial bootstrapping,
the host will not aware changes of cassandra.inital_token. If I want add a new token( virtual
node), I have to rebuild the host with new token list.
> 
> My question is if there is way to add a virtual nodes without rebuild it?
> 
> Thanks,
> 
> On Jan 30, 2013, at 10:21 AM, Manu Zhang wrote:
> 
>> On Wed 30 Jan 2013 02:29:27 AM CST, Zhong Li wrote:
>>> One more question, can I add a virtual node manually without reboot
>>> and rebuild a host data?
>>> 
>>> I checked nodetool command, there is no option to add a node.
>>> 
>>> Thanks.
>>> 
>>> Zhong
>>> 
>>> 
>>> On Jan 29, 2013, at 11:09 AM, Zhong Li wrote:
>>> 
>>>> I was misunderstood this
>>>> http://www.datastax.com/dev/blog/virtual-nodes-in-cassandra-1-2 ,
>>>> especially
>>>> "If you want to get started with vnodes on a fresh cluster, however,
>>>> that is fairly straightforward. Just don’t set the
>>>> |initial_token| parameter in your|conf/cassandra.yaml| and instead
>>>> enable the |num_tokens| parameter. A good default value for this is 256"
>>>> 
>>>> Also I couldn't find document about set multiple tokens
>>>> for cassandra.inital_token
>>>> 
>>>> Anyway, I just tested, it does work to set  comma separated list of
>>>> tokens.
>>>> 
>>>> Thanks,
>>>> 
>>>> Zhong
>>>> 
>>>> 
>>>> On Jan 29, 2013, at 3:06 AM, aaron morton wrote:
>>>> 
>>>>>> After I searched some document on Datastax website and some old
>>>>>> ticket, seems that it works for random partitioner only, and leaves
>>>>>> order preserved partitioner out of the luck.
>>>>> Links ?
>>>>> 
>>>>>>  or allow add Virtual Nodes manually?
>>>>> If not looked into it but there is a cassandra.inital_token startup
>>>>> param that takes a comma separated list of tokens for the node.
>>>>> 
>>>>> There also appears to be support for the ordered partitions to
>>>>> generate random tokens.
>>>>> 
>>>>> But you would still have the problem of having to balance your row
>>>>> keys around the token space.
>>>>> 
>>>>> Cheers
>>>>> -----------------
>>>>> Aaron Morton
>>>>> Freelance Cassandra Developer
>>>>> New Zealand
>>>>> 
>>>>> @aaronmorton
>>>>> http://www.thelastpickle.com <http://www.thelastpickle.com/>
>>>>> 
>>>>> On 29/01/2013, at 10:31 AM, Zhong Li <zli@voxeo.com
>>>>> <mailto:zli@voxeo.com>> wrote:
>>>>> 
>>>>>> Hi All,
>>>>>> 
>>>>>> Virtual Nodes is great feature. After I searched some document on
>>>>>> Datastax website and some old ticket, seems that it works for
>>>>>> random partitioner only, and leaves order preserved partitioner out
>>>>>> of the luck. I may misunderstand, please correct me. if it doesn't
>>>>>> love order preserved partitioner, would be possible to add support
>>>>>> multiple initial_token(s) for  order preserved partitioner  or
>>>>>> allow add Virtual Nodes manually?
>>>>>> 
>>>>>> Thanks,
>>>>>> 
>>>>>> Zhong
>>>>> 
>>>> 
>>> 
>> 
>> You add a physical node and that in turn adds num_token tokens to the ring.
> 


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