Network Connectivity Distance
 

Between two clustered networks in the same building how far away is too far before there is a slight degrade in the quality of communication between the two clusters?

I'm not sure about the distance, do you have data in local drive or in SAN? You need to consider everything.

The answer to this question depends on a lot of factors besides just the distance between both the clusters. The means of communication is the most important factor here which can either be very good or really hamper your options. I believe that you should consult someone who helped design that network originally in your company.