What are the guidelines around allocating storage space for AMS service?
A partner is looking for ballpark number for a small / medium and large cluster so they can ensure that they don't run out of storage space for AMS
Please see the above. You want to make sure that it's pointing to correct file system with enough space. I would say 200GB to 300GB dedicated disk is good start for small cluster. Many times, installation ends up on root thats why its important to pay attention to the above setting.
While storage space is absolutely critical as @Neeraj Sabharwal and @Ali Bajwa wrote in their post we just "discovered" that also CPU is a key point. When HWX released AMS we began to deploy Ambari and AMS on the same machine, but soon the understood that for a production environment it could be a good practice to use one VM for Ambari and another VM for AMS, so the really high impact on computation resources of AMS didn't impact Ambari (sometimes, during the aggregation phase we got 16 CPU at 90% for 10/15 minutes).