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From Carlos Alonso <i...@mrcalonso.com>
Subject Re: Property file snitch and unbalanced cluster
Date Fri, 28 Oct 2016 08:49:05 GMT
Hi Robert,

What has happened is that you have now two datacenters in your cluster. The
way they replicate information will depend on your keyspace settings.

Regarding your process I don't think it is safe to do it that way. I'd
start off by decommissioning nodes 4 and 5 so that your cluster is back to
1 datacenter with 3 nodes and then add them sequentially again making sure
the configuration in the Snitch is the proper one.

Regards.

Carlos Alonso | Software Engineer | @calonso <https://twitter.com/calonso>

On 28 October 2016 at 10:06, Robert Sicoie <robert.sicoie@gmail.com> wrote:

> Hi guys,
>
> I have a cluster with 5 nodes, cassandra 3.0.5, RF=2, PropertyFileSnitch.
> Three of the nodes were added initially, DC=PRD. The other two were added
> more recently.
>
> The default for unknown nodes default=DC1:r1 (which is bad in my case, as
> it would have been nice to have PRD as default)
>
> As the three initial do not have the information about the later two in
> the properties file, they see node4 and node5 as in DC1:r1.
>
> I assume that:
>
>    - 1-2-3 have mode data than 4 and 5 because all writes that come to
>    1-2-3 are replicated only on 1-2-3 (as there is no schema for DC1) and this
>    is why 1,2,3 have more data and the cluster is unbalanced.
>    - all writes that come to 4 and 5 are replicated on 1,2,3,4 and 5 as
>    the property file snitch config has info about the entire cluster on 4 and
>    5.
>
> Is it save if I just update the network topology file on 1, 2, 3 and add
> lines about node 4 and 5, and then roll restart 4 and 5? Will the cluster
> balance itself? Currently 1, 2, 3 have about 16GB each and 4,5 about 6 GB
> each.
>
> Thanks,
>
> Robert
>

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