Look to your limits.conf for the answer, that's what solved the problem for us. Specifically you may need to lower your base_max_searches if you have it defined. We also used the max_searches_perc parameter for the [scheduler] stanza to help limit the amount of searches that the Search Head was issuing to the Indexer at a given time.
Here is a quick look at our settings now that are working nicely, obviously you'll want to adjust these to something that makes sense for your architecture.
[search]
multi_threaded_setup = 1
base_max_searches = 64
[metadata]
maxcount=500000
[scheduler]
max_searches_perc = 10
... View more
