139 research outputs found
Executing Bag of Distributed Tasks on the Cloud: Investigating the Trade-offs Between Performance and Cost
Bag of Distributed Tasks (BoDT) can benefit from decentralised execution on
the Cloud. However, there is a trade-off between the performance that can be
achieved by employing a large number of Cloud VMs for the tasks and the
monetary constraints that are often placed by a user. The research reported in
this paper is motivated towards investigating this trade-off so that an optimal
plan for deploying BoDT applications on the cloud can be generated. A heuristic
algorithm, which considers the user's preference of performance and cost is
proposed and implemented. The feasibility of the algorithm is demonstrated by
generating execution plans for a sample application. The key result is that the
algorithm generates optimal execution plans for the application over 91\% of
the time
Allocation of Virtual Machines in Cloud Data Centers - A Survey of Problem Models and Optimization Algorithms
Data centers in public, private, and hybrid cloud settings make it possible to provision virtual machines
(VMs) with unprecedented flexibility. However, purchasing, operating, and maintaining the underlying physical
resources incurs significant monetary costs and also environmental impact. Therefore, cloud providers must
optimize the usage of physical resources by a careful allocation of VMs to hosts, continuously balancing between
the conflicting requirements on performance and operational costs. In recent years, several algorithms have been
proposed for this important optimization problem. Unfortunately, the proposed approaches are hardly comparable
because of subtle differences in the used problem models. This paper surveys the used problem formulations and
optimization algorithms, highlighting their strengths and limitations, also pointing out the areas that need further
research in the future
CLOSURE: A cloud scientific workflow scheduling algorithm based on attack-defense game model
The multi-tenant coexistence service mode makes the cloud-based scientific workflow encounter the risks of being intruded. For this problem, we propose a CLoud scientific wOrkflow SchedUling algoRithm based on attack-defensE game model (CLOSURE). In the algorithm, attacks based on different operating system vulnerabilities are regarded as different “attack” strategies; and different operating system distributions in a virtual machine cluster executing the workflows are regarded as different “defense” strategies. The information of the attacker and defender is not balanced. In other words, the defender cannot obtain the information about the attacker’s strategies, while the attacker can acquire information about the defender’s strategies through a network scan. Therefore, we propose to dynamically switch the defense strategies during the workflow execution, which can weaken the network scan effects and transform the workflow security problem into an attack-defense game problem. Then, the probability distribution of the optimal mixed defense strategies can be achieved by calculating the Nash Equilibrium in the attack-defense game model. Based on this probability, diverse VMs are provisioned for workflow execution. Furthermore, a task-VM mapping algorithm based on dynamic Heterogeneous Earliest Finish Time (HEFT) is presented to accelerate the defense strategy switching and improve workflow efficiency. The experiments are conducted on both simulation and actual environment, experimental results demonstrate that compared with other algorithms, the proposed algorithm can reduce the attacker’s benefits by around 15.23%, and decrease the time costs of the algorithm by around 7.86%
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