Quality of Service (QoS) is essential to datacenters, which requires effective schemes to manage the flows among numerous servers. However, existing management techniques mainly focus on the QoS issues over Internet. This paper presents a Dynamic Feedback Control flow management model for datacenters, called DFC, to achieve performance improvement and fault-tolerance. Based on the new model, mechanisms derived from feedback control are designed and evaluated. By observing system status of each server in the datacenter, DFC successfully applies a smart resources distribution policy and resiles when node breaks down. Preliminary experiments are carried out to validate the effectiveness of the model, based on both the NS2 simulation platform and a datacenter prototype. Evaluation results demonstrate that DFC can effectively improve datacenter's performance and guarantee a good reliability.