node data migration

Grant Schofield grant at basho.com
Tue May 4 17:05:36 EDT 2010


There would be 2 ways to such an upgrade. 

You could backup the node and shut it down cleanly. Other nodes in the cluster will take over for the shutdown node as long as your R, N , and W values were able to cope with the change. If you make a copy of your data directory, including the ring and data store directory, you could put them back in place and start the node as normal after the upgrade. This is predicated on you not changing the node name (IP), but if you did want to change it you could use the reip feature.  This is probably the easiest way to do the upgrade, but if your cluster is small I would recommend the second method

The second way would be to tell the node to leave the cluster. This will transfer all of the data out of the node to several different nodes which will take its place in the ring.  Currently this can only be done via a bin/riak attach command. Run the following:
    {ok, C} = riak:local_client(),
    Res = C:remove_from_cluster(node()),
    io:format("~p\n", [Res]).

Once the node leaves the cluster and hands off all of its partitions you should see the data directory get smaller and empty out completely once all of the data has handed off to other nodes.   Once you do the upgrade you can setup a new Riak node on the host, start it, and join the cluster just like you would any other new node.

Thanks,
Grant Schofield
Developer Advocate
Basho Technologies


On May 4, 2010, at 3:02 PM, Matthew Pflueger wrote:

> Scenario:  I need to upgrade the OS of my nodes in my cluster which
> will result in a reboot of each node.  What would be the process to
> nicely migrate data away from each node?
> 
> If my understanding is correct, performing a nice shutdown of a riak
> node via `riak stop` will migrate the data away from the node.  Am I
> correct?  If so, approximately how long would it take to do the
> migration if say each node represents 1 gig of data?  Does that whole
> gig get migrated away or only the data that is not replicated?
> 
> 
> --Matthew
> 
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