Your understanding of nodetool cleanup is not correct. cleanup is used only after cluster balancing like adding or removing nodes. It removes data that does not belong on the node anymore (in older versions it removed hints as well)

Your debate is needing to run companion . In a write only workload you should let cassandra do its normal connection.(in most cases)

On Wednesday, November 30, 2011, David McNelis <dmcnelis@agentisenergy.com> wrote:
> In my understanding Cleanup is meant to help clear out data that has  been removed.  If you have an environment where data is only ever added (the case for the production system I'm working with), is there a point to automating cleanup?   I understand that if we were to ever purge a segment of data from our cluster we'd certainly want to run it, or after added a new node and adjusting the tokens.
> So I want to make sure I'm not missing something here and that there  would be other  reasons to run cleanup regularly?
>
> --
> David McNelis
> Lead Software Engineer
> Agentis Energy
> www.agentisenergy.com
> c: 219.384.5143
> A Smart Grid technology company focused on helping consumers of energy control an often under-managed resource.
>
>