Dear Tanvir,

I suggest to you links, attached files

-Scalable Stochastic Models for Cloud Services - DukeSpace

https://dukespace.lib.duke.edu/dspace/handle/10161/6110

-Resource Management in Utility and Cloud Computing

https://books.google.dz/books?isbn=1461489709

-Resource Management and Efficiency in Cloud Computing Environments

https://books.google.dz/books?isbn=1522517227

-Cloud Computing Advancements in Design, Implementation, and Technologies

https://books.google.dz/books?isbn=1466618809

Best regards

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This is a very good question.   In addition to the excellent answer given by @Mohamed-Mourad Lafifi, there is a bit more to add.

In cloud computing, an element of uncertainty is inherent.   In other words, uncertainty is a persistent characteristic of cloud computing.   Hence, the stochastic nature (seemingly random probability distributions) is a biproduct of cloud computing.

Exploration of the uncertainty assocated with cloud computing is explored in

https://www.researchgate.net/publication/277919460_Towards_Understanding_Uncertainty_in_Cloud_Computing_Resource_Provisioning

Article Towards Understanding Uncertainty in Cloud Computing Resourc...

Dear Tanvir, I'm working with systems for the past several years. Since my first year on university from then to now on as a research fellow. I got different experiences through working and would love to share with you. Most of the systems follow random probability distributions because of their different work aspects in different time distribution processes. Time is the most significant dependent metric for every systems. By varying different workloads  systems have to follow different queuing theories or models.

To know more you have to read or gone through the papers that are given above by Sir James F Peters andSir Mohamed-Mourad Lafifi. Some of mine are given below as an attachment.

http://www.ijrcct.org/index.php/ojs/article/viewFile/1253/pdf

Thanks a lot Sir Mohamed-Mourad Lafifi , Sir James F Peters and Md.Julkar Nayeen Mahi for your valuable suggestions.