The placement of the virtual machines in a Hyper-V cluster is an important step to ensure performance and high availability. To make a highly available application, usually a cluster is deployed spread across two or more virtual machines. In case of a Hyper-V node is crashing, the application must keep working.
But the VM placement concerns also its storage and its network. Let’s think about a storage solution where you have several LUNs (or Storage Spaces) according to a service level. Maybe you have a LUN with HDD in RAID 6 and another in RAID 1 with SSD. You don’t want that the VM which requires intensive IO was placed on HDD LUN.