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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Adjusting Token Spaces and Rebalancing Data
Date Mon, 01 Mar 2010 22:54:59 GMT
On Mon, Mar 1, 2010 at 3:18 PM, Jon Graham <sjcloud22@gmail.com> wrote:
> Thanks Jonathan.
>
> It seems like the load balance operation isn't moving. I haven't seen any
> data file time changes in 2 hours and no location file time
> changes in over an hour.
>
> I can see a tcp port # 7000 opened on the node where I ran the loadbalance
> command. It is connected to
> port 39033 on the node receiving the data. The CPU usage on both systems is
> very low. There are about 10
> million records on the node where the load balance command was issued.

Did you check logs for exceptions?

> My six node Cassandra ring consists of tokens for nodes 1-6 of:  0
> (ascii 0x30)  6  B  H  O (the letter O)  T
>
> The load balance target node initially had a token of 'H' (using ordered
> partitioning). The source node has a key of 0 (ascii 0x30). Most of the data
> on the source node has keys starting with '/'. Slash falls between tokens T
> and  0 in my ring so most of the data landed on the node with token 0 with
> replicas on the next 2 nodes. My token space is badly divided for the data I
> have already inserted.
>
> Does the initial token value of the load balance target node selected by
> Cassandra need to be cleared or set to a specific value before hand to
> accomodate the load balance data transfer?

No.

> Would I have better luck decommissioning nodes 4,5,6 and trying to
> bootstrapping these nodes one at a time
> with better initial token values?

LoadBalance is basically sugar for decommission + bootstrap, so no.

> I am looking for a good way to move/split/re-balance data from nodes 1,2,3
> to nodes 4, 5, 6 while achiving a better token space distribution.

I would upgrade to the 0.6 beta and try loadbalance again.

-Jonathan

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