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From Sylvain Lebresne <sylv...@yakaz.com>
Subject Re: What is loadbalance supposed to do? 0.6.0RC1
Date Wed, 07 Apr 2010 14:06:56 GMT
> It shouldn't remove a node from the ring should it?  (appears it did)

It does. As explained here: http://wiki.apache.org/cassandra/Operations,
loadbalance 'decomission' the node and then add it back as a bootstrapping
node (roughly).

So that the node disappear is expected and it is supposed to come back.
But this is not a quick operation (and certainely not one you want to do every
other day). You apparently restarted Cassandra while it was doing its stuff.

Not sure the loss of data is to be expected though.

> It shouldn't remove data from db, should it?  (data size appears to grow, but records
are now missing)
>
> Loaded 38 million "rows" and the ring looked like this:
>
>  mark@ec2:~/cassandra/apache-cassandra-0.6.0-rc1$ bin/nodetool --host 192.168.1.116
ring
>  Address       Status     Load          Range                    
                 Ring
>                                         167730615856220406399741259265091647472
>  192.168.1.116 Up         4.81 GB       54880762918591020775962843965839761529
    |<--|
>  192.168.1.119 Up         12.96 GB      160455137948102479104219052453775170160
   |   |
>  192.168.1.12  Up         8.98 GB       167730615856220406399741259265091647472
   |--
>
> So I did this:
>  mark@record:~/cassandra/apache-cassandra-0.6.0-rc1$ bin/nodetool --host 192.168.1.12
loadbalance
>
> And this happened (even though Cassandra was still running):
>
>  mark@record:~/cassandra/apache-cassandra-0.6.0-rc1$ bin/nodetool --host 192.168.1.12
ring
>  Address       Status     Load          Range                    
                 Ring
>                                         160455137948102479104219052453775170160
>  192.168.1.116 Up         12.71 GB      54880762918591020775962843965839761529
    |<--|
>  192.168.1.119 Up         13.47 GB      160455137948102479104219052453775170160
   |-->|
>
> After restarting Cassandra on .12
>
>  mark@record:~/cassandra/apache-cassandra-0.6.0-rc1$ bin/nodetool --host 192.168.1.12
ring
>  Address       Status     Load          Range                    
                 Ring
>                                         160455137948102479104219052453775170160
>  192.168.1.116 Up         12.71 GB      54880762918591020775962843965839761529
    |<--|
>  192.168.1.12  Up         8.98 GB       107669873051407416105654071439122680093
   |   |
>  192.168.1.119 Up         13.47 GB      160455137948102479104219052453775170160
   |-->|
>
> Now I have more data, but nearly 50% of my queries are failing (not found).  This data
was checked before the load balance was done.
>

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