Question

If I deploy reports to an SSRS portal, then the aggregations and rendering are all taken care of by the report server, not locally when I run the report right?

Answer 1

Short answer:
Yes, report server usually processes the reports deployed on portals.

Long answer:
If you have:

1. A report server
2. A portal server
3. A client pc accessing the portal

Then depending on what you’re doing the report’s processed in a different place:

• With remote processing the report will be done on the report server (1).
• Using local processing the report will be done on the portal server (2).
• When previewing a report in your designer the report’s processed on your local pc (3).

Note that although aggregations in the report (the ones in tablixes) are handled by the machine processing the report, aggregations in the SQL (such as GROUP BY) for the datasets will be handled by the server processing the dataset, which is often SQL server.