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From Jon Graham <sjclou...@gmail.com>
Subject Re: Adjusting Token Spaces and Rebalancing Data
Date Mon, 01 Mar 2010 21:18:52 GMT
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.

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?

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?

Would the existing data on nodes 1,2,3 be moved to the boot strapped nodes?

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.

Thanks for your help,
Jon


On Mon, Mar 1, 2010 at 11:55 AM, Jonathan Ellis <jbellis@gmail.com> wrote:

> On Mon, Mar 1, 2010 at 1:44 PM, Jon Graham <sjcloud22@gmail.com> wrote:
> > Can I tell if the load balancing operaion is still running ok or if it
> > has terminated?
> >
> > Is there a rough computation to determine how long the process should
> take?
>
> Not really, although you can guess from cpu/io usage.  This is much
> improved in 0.6.
>
> > If the load balancing is successful, will the cluster ring
> > information reflect the load balanacing changes?
>
> Yes.
>

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