Nowadays dynamic service management frameworks are proposed to ensure end-to-end QoS. To achieve this goal, it is necessary to manage Service Level Agreements (SLA) which specify quality parameters of the services operation such as availability and performance. This work is focused on video-on-demand (VoD) services to investigate the goodness of performability techniques in end-to-end QoS scenarios. Based on a straightforward Markov Chain, Markov-Reward Chain (MRC) models are developed in order to obtain various QoS measures of an adaptive VoD service. The MRC model has a clear understanding with the design and operation of the VoD system. In this way, several design options can be compared. To compute performability measures of the MRC model, the randomization method is employed. Predicted model results fits well with the ones taken from a real video-streaming testbed.