Keeping SAS and Hadoop in save Realm is a good Idea to simplify configuration and setup, but there are other important considerations as well. Performance is one important consideration. As your cluster grows, volume of AS and TGS interaction will also grow, consider this volume while making a decision to use KDC for hadoop and SAS. Troubleshooting process around Kerberos related issues will need to engage both Hadoop and SAS admin teams. Another alternative may be to have local KDC for both and use cross realm trust. Haven't tried this and not sure about complexities around but it may be a good option if works. I do also explore things and have written about implementing Kerberos in Hortonworks cluster at http://bit.ly/1LLAUJZ