Logistics battalions were components that belonged to the Grand Army of the Republic, overseeing the intricate task of delivering reinforcements and supplies to the GAR's combat units. In conjunction with Fleet Ops, they received continuous updates from the Logistics center located at Coruscant Command HQ regarding the military's supply chain situation.
Despite being affiliated with the GAR's clone forces, the available information does not explicitly state that the individuals within the Logistics battalions were clone troopers; it's possible they were reassigned from the Judicial Department or regional defense forces.