The first domain controller in the first Active Directory forest will hold all five FSMO roles. All these roles are critical in the Active Directory infrastructure. Some of them are heavily used and some roles are only used only on specific occasions. Some role owners will not be able to afford any downtime, and some roles will still be able to have downtime. So, based on characteristics, impact, and responsibilities, these can be placed on different domain controllers. FSMO roles placements are based on certain facts that are listed in the next section.