الفهرس 
Chapter (1) IntroductionOnly 14 pages are availabe for public view
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Abstract
Cloud Computing refers to scalable and virtualized resources provided as a services through the internet . Cloud services allow users to access information and computer resources at any time and any place provided that network connection is available. Cloud computing technology has many benefits including cost savings, service flexibility and high availability.
The likelihood of failures rises in Cloud Computing systems due to its heterogeneous nature as compared to other parallel computing environments. These failures have a high impact on cloud performance and the expected benefits for both customers and providers. Therefore, a fault-tolerant service must be included to detect errors and recover from them and thus avoiding these failures in the cloud. Checkpointing is one of the most known reactive fault tolerance techniques used in distributed computing.
This thesis proposes ”Reactive Approach With Flexible Checkpoint Interval” to tolerate faults in cloud computing systems. This approach depends on applying a flexible interval of the checkpoint to reduce overheads.
In the proposed approach, the failure percentage of servers that accommodate virtual machines determines the Checkpoint interval. Therefore, the value of the Checkpoint interval will inconstantly change from time to time and there will be no fixed value for it or even fixed values for its change.
Our proposed approach is compared with other two checkpoint-based approaches. The first approach applies number of failures and changes the value of the length of the Checkpoint interval with static values. The other approach uses a fixed value for the length of the checkpoint interval.
Simulation experiments have been conducted to evaluate our approach. The experimental results show that the proposed approach outweighes performance of the other approaches in terms of response time, power consumption, monetary cost and cloud capacity.