Third, the Quality-of-Service (QoS) of big data tasks has not been considered in existing work.
Similar to conventional cloud services, big data applications also exhibit Service Level-Agreement (SLA) between a service provider and the requesters.
To observe SLA, a certain level of QoS, usually in terms of task completion time, shall be guaranteed.
The QoS of any cloud computing tasks is first determined by where they are placed and how many computation resources are allocated.
Besides, the transmission rate is another influential factor since big data tasks are data-centric and the computation task cannot proceed until the corresponding data are available.
Existing studies, e.g., [3], on general cloud computing tasks mainly focus on the computation capacity constraints, while ignoring the constraints of transmission rate.