Assuming you're on a recent version of Splunk, hit Settings in the top right corner and open the Distributed Management Console, big green icon.
DMC should be the best option, but it will only show your environment correct if all internal logs are forwarded to the indexers and the Splunk instance running DMC has all indexers as search peer, see the docs for more detail http://docs.splunk.com/Documentation/Splunk/6.3.0/DMC/DMCoverview
Hi.. yes... Best would be to use the S.o.S Splunk app. It should provide what you need and more. You can also search internal index(depending on your environment/search head configuration). Eg: Something like
index=_internal earliest=-30m per_index_thruput will give you info on the data received from various hosts in the past 30 min from indexers responding to your search head... check out the available Fields and tweak the search per your requirement. You do this on Web or Use CLI /REST.