Check the ClearPass Scaling & Ordering Guide for more specific capacity information.
From that: "Virtual appliances require similar resource specifications to ensure a consistent ClearPass experience regardless of hardware or virtual appliance."; so with the correct specifications and (reserved) resources (CPU/mem/disk), the VM should perform similar to it's hardware appliance equivalent.
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Herman Robers
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If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check
https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
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