Dante,
Because you're looking to collect performance data historically the Performance Advisor tool that comes with OnCommand 5.x Unified Manager is what you'd want. This software is free to all NetApp customers. It will monitor IOPS information at the controller, aggregate, volume and LUN level. It keeps performance data historically, so you can view and analyze it over an hour, day, week, month, etc... There is a built-in statistical metrics tool that allows you to see minimum, maximum, mean and percentile values for your historical performance. You can also easily export this historical data out to CSV format so you can analyze it using other tools like SAS or Excel.
Contact your sales team about how to get OnCommand Unified Manager software. They'll have to order a license key for you, but it's zero cost to you.
If you won't want to install software to accomplish this, check out the following article. It is an article on how to manually way collect the same performance stats directly from the controller. However, you'd have to figure out a way to run it for a week and store the data somewhere.
https://communities.netapp.com/groups/chris-kranz-hardware-pro/blog/2009/04/01/performance-stats-without-perfstat-or-ops-mgr
