Plesk has a basic Statistics package built in that you can use to analyse traffic to your site/server. You'll need to enable it for any Subscriptions that you would like to track. To do this, please follow this guide:
1. First you need to Log in to your Plesk control panel.
2. Click on 'Subscriptions' -> (domain name).
3. Click on the Statistics tab.
3. This will display all the stats for your site, disk usage, FTP and visitor stats