The recommended current practice for clustered Hyper-V host maintenance is to live migrate all VMs on the target host to a different host. This practice also applies if you utilize the SCVMM host migration features of dynamic and power optimization.
Live migration and dynamic and power optimization will normally happen successfully in the background. Any VMs with ISO images attached during either of these tasks will not successfully migrate. The result of a failed migration in either case is possible downtime or degraded performance.
This recipe will show you how to automate the location and removal of attached ISO images on a predefined schedule.