IBM on Hyper-V: eligibility and pitfalls.
Microsoft Hyper-V is recognized virtualization technology for IBM sub-capacity licensing, but the eligibility is conditional and the counting rules are specific. Get the configuration or the tooling wrong and IBM charges for the full physical host rather than the cores your software actually uses.
Hyper-V estates are a frequent source of full-capacity findings, not because the platform is ineligible, but because the conditions that make sub-capacity hold are easy to break without noticing. When an audit lands, the question is never simply "do we run Hyper-V." It is whether each in-scope product was eligible, whether the host was configured within the rules, and whether the IBM License Metric Tool was recording it correctly the whole time.
Hyper-V is eligible technology, with conditions
IBM publishes Hyper-V on its list of eligible virtualization technologies for sub-capacity counting. That means a qualifying product running in a Hyper-V virtual machine can, in principle, be licensed on the virtual cores assigned to it rather than every core in the physical server. The principle only survives if the supporting conditions hold.
The product must itself be sub-capacity eligible
Eligibility is decided product by product. Most of the high-risk middleware that draws audits qualifies, but the platform being eligible does nothing for a product that is full-capacity only. Confirm each product against the published eligible list before assuming Hyper-V buys you anything.
The virtual machine must be capped, not just sized
Sub-capacity counts the virtual cores made available to the guest. If a virtual machine can burst beyond its nominal allocation, IBM counts the maximum it could reach, not the average it ran at. A loosely configured guest that can expand across the host quietly turns into a full-capacity claim.
A product using 4 virtual cores on a 32 core Hyper-V host is 480 PVU under sub-capacity. Defaulted to full-capacity because the tooling lapsed or the guest was uncapped, the same deployment is 3,840 PVU, eight times the number, with no change to the software itself.
The pitfalls that void the sub-capacity claim
- ILMT not deployed within 90 days of the first eligible Hyper-V deployment, or not running continuously across the period.
- Quarterly sub-capacity reports not generated and retained for the required two years.
- Broken or missing ILMT agents on Hyper-V guests, which void the sub-capacity claim for the affected period.
- Live migration moving guests across hosts without the inventory tool tracking the movement, leaving capacity uncounted.
- Guests running on a host release outside the eligible technology list, which removes eligibility regardless of the product.
Each of these is recoverable to a degree, but only with evidence. The ILMT record, the report archive, and the host configuration history are what convert an apparent full-capacity exposure back to the sub-capacity number. Reconstructing them after the auditor has already applied full-capacity is far harder than maintaining them in advance.
Hyper-V does not protect you on its own. Sub-capacity on Hyper-V holds only when the product is eligible, the guest is properly capped, and ILMT recorded it continuously with retained reports. Verify all three before the data leaves your network, because IBM will default any gap to full-capacity for the whole host.