Welcome to the community @DLPnewb. Your question requires some background and you have provided a good deal already.
I have assumed:
as per Treesize you have a single tier install (Console, Management Server {MS}, Indexer & collector on one node) this indicates a smaller environment
as per the retention policy you keep all data for 1 year
Unknowns:
Whether you have added exclusions to your dataset to reduce the data collected from scanning and events.
(for example you may still be collecting events for the service ID that runs scans, the backup user ID or events on routine tasks you need not track)
The size of the environment, number of filers, and shares scanned.
The current version you are running.
Comments:
The latest version for Symantec DataInsight (SDI) is 3.0.1RP6 which can be downloaded from here. This is a Rolling Patch and has many features that will assist in reducing the footprint of the data. Your strategy should be to install the latest version then reduce the dataset using exclusions (on your web browser enter https://<SDI MS Name>/symhelp/CS.do?ProdId=SDISYMHELPV_301&vid= and search 'exclude') or remove some report archives (Report tab from black bar, report from the list on the left, individual report listed, click "Select Action...' and choose Delete) to remove the report. You will have to rerun the report again to access it from the server but can save a copy in one of the available formats elsewhere. Do not delete the report data from the reportrun folder as there is a hierarchy that is required with the format of a parent structure of S:\DataInsight\data\console\reports\reportruns\ #s with a range of 1-999 or a very large number for differing types of reports.
Hopefully this is answer to your question but if you need assistance with the configuration, please contact my colleagues at Symantec Technical Support for assistance.
Rod
