Bug ID 6742805: A domain shutdown or memory scrub can take over 15 minutes with a single CPU and a very large memory configuration. During a shutdown, the CPUs in a domain are used to scrub all the memory owned by the domain. The time taken to complete the scrub can be quite long if a configuration is imbalanced, for example, a single CPU domain with 512 Gbytes of memory. This prolonged scrub time extends the amount of time it takes to shut down a domain.
Workaround: Ensure that large memory configurations (>100 Gbytes) have at least one core. This results in a much faster shutdown time.