How to perform Perforamance Test for the Scenario

I have to test one client server application. The scenario is, client continuously monitors the users system and sends the required data to the server. During this, client stores the data in a file on the c drive of local machine. How this application can be tested for the 500 users(separate nodes should be created as data gets stored in a single file on c drive). Please guide me if anybody has idea about this.

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