The Research On Reliability Evaluation Model And Key Technologies Of Cloud Service

As an important intrinsic attribute to measure the quality of service, the reliability canreflect the capability of service system to provide reliable service continually from the use’spoint of view. Cloud computing is providing the virtualization application computing resource tousers with the idea and form of everything as a service. The cloud service mode basing on theService-Oriented Architecture, has transformed the whole software framework from “softwareequal to programmer adding data and document” to “software equal to service adding workflowand data”, the software development methodology has changed from the traditionaryproduct-oriented to service-oriented, the software running environment has transferred fromclose, static and controllable to open, dynamic and levity. The service’s scale, complexity,difficulty, dynamism and novelty of various application fields bring the huge impact andchallenge to the development of reliability. The reliability has been the most require immediatelybreakthrough issues in the cloud service field, its essentiality and urgency has not to be ignored.With the cloud service computing model, the cloud computing and reliable engineering arefaced with two challenging tasks, one is how to use existing cloud services to build up highlyavailable and reliable services to make sure that the services will go along with the anticipatedtrajectory, and towards to the anticipated target, the other is how to design a reliable cloudservice objective and scientific, and evaluate the reliability of the cloud service dynamic andeffective. The characteristics of Cloud service such as super large scale, high complexity,multiple failure modes, virtualization and resource dynamic changes etc.，which have made thetraditional reliability evaluation model fail to accommodate the new features and new demandsof the cloud service. In view of the problem existing in the reliability evaluation of cloud serviceas well as service composite, this thesis is aiming to study systematically on the system structure,application model, technology, guarantee mechanism and the key technology of specificimplementation of cloud services composite reliability evaluation, based on the overall analysisof the system structure and service oriented architecture of the reliability evaluation model. Themain contributions of this paper are divided into four aspects as follows:(1) This paper first analyses the characteristics of cloud service technology, the relevanttheories and research status of reliability evaluation, and summarizes the models and methods ofreliability evaluation. Also, it points out the main problems that currently existing, and putsforward the reliability assessment modeling theories and methods of cloud service.(2) In view of the drawbacks in the reliable cloud service coordinate application providedby the current reliability evaluation model, which is under the dynamic, complex and changeablecloud service conditions, this thesis proposes a reliability evaluation model of cloud servicebased on variable weights (REMCSVM). According to the application characteristics of IaaS,PaaS and SaaS cloud service, the reliability evaluation index stratification architecture of cloudservice is established, the hierarchy analytic structure of the reliability model is built, and thereliability framework of cloud service is put forward. In reference to the thought of AHP variableweights, the failure correlation relationships of hierarchy cloud service is ascertained, the reliability importance weights value between each layer services is given a quantitative analysisusing the related principles of triangle fuzzy number, and a new weights value order calculatingmethod is given out by the triangle fuzzy complementary judgment matrix. In addition,combined with the online monitoring reliability data of cloud service system in each level ofcloud services, the reliability evaluation calculating formulas of Cloud Services is put forward.(3) With the reliability requirements of composite services based on BPEL businessprocesses, a two-dimensional and multi-levels reliability evaluation model of cloud servicecomposition is presented. Found on the characteristics of the business process management, animplementation framework of composite cloud service based on BPEL. Based on the theory andmodeling methods of stochastic Petri nets, the methods for the transformation from the BPELbusiness process to the composite cloud service process net model is discussed. In view of theidea of SOA and the dynamic changeable requirements, a two-dimensional and multi-levelsreliability evaluation framework of cloud service composite is designed, and the reliabilityanalysis method based on Markov process and the reliability dynamic assessment method basedon equivalent reduction is introduced.(4) In allusion to the redundant features and reliability guarantee requirements, this thesistries to explore the effective ways for improving cloud service reliability, and a reliabilityoptimization method of cloud service based on trust redundancy is proposed. On the basis ofcomprehensive analysis of fault-tolerant algorithm, based on the application architecture of thecloud services, a trust redundancy reliability enhancement framework of cloud service is putforward. Based on the failure polling detection algorithm of voting protocol, a trust-awarefault-tolerant service selection algorithm is designed, and the calculation methods of minimumnumber of fault-tolerant services is given. Based on the running fault-tolerant managementframework of services combination, a cloud service invoking policy of ensuring service responsetime based on failure rules is presented.