Estimating Splunk storage requirements per input

[Itisfun33]

In Splunk 4.1.5 we are attempting to estimate our storage requirements per input, with the ultimate purpose of splitting our indexing up into 1 index per input. So naturally we need to know how much space each application is costing in our current unorganized indexes first. We can get the total space used, but how would you suggest finding out how much hard drive space each input is currently using?

Thank you for your input and your assistance!

[jharty_splunk]

In the search app Index Activity -> Index Volume.
From here you can review the volume usage by host,source and sourcetype.

As a general rule compression rate is about 40% or your uncompressed raw data. Index=(10-15% compressed raw data, 25-30% metadata indexes).