How on a single-instance Splunk Enterprise\ES search head\indexer can I define the volume of License that is used by ES in order to plan upgrade. Should I count volume of data used by ES Add-Ons?
Or this is actual when we have separate instance for ES?
Your ES license is based on your Splunk Enterprise license... so if you've got 100GB of Splunk license, your ES license will be calculated at 100GB.
If you intend to add data while rolling out ES you can add the data to a testing instance for a few days and see how much you get, as you would when adding data to Splunk Enterprise without ES.
Hi, do I understand correctly - if I have perpetual ES and perpetual Splunk Enterprise licensed and want to upgrade Splunk Enterprise - than I need also upgrade License ES to the same amount?
That would be the way to go, yes.
Do keep in mind though, for detailed licensing discussions you should also talk to your local partner or Splunk sales representative.