the following comment in the code describes them very clearly: 

*   LOCAL_QUORUM Returns the record with the most recent timestamp once a majority of replicas within the local datacenter have replied.
 *   EACH_QUORUM  Returns the record with the most recent timestamp once a majority of replicas within each datacenter have replied.


but it seems that my intended use case is not solved by either policy:
I have 2 colos,  mostly I want to run my application in the primary-backup (or "hot/warm" ) mode, though everything is automated, and a human "switch over" is not needed in case of one colo failure. I want all writes/reads to get a quorum from local colo,  then at least make sure that 1 write has propagated to the other colo.

So I do not necessarily need a Quorum from remote colos, but I need at least one write to arrive there.

does that sound like a common use case? within the current code, is there a way to achieve that? if not, creating a new policy does not seem too difficult either.

Thanks
Yang