# A Dynamic Decision Support System for Selection of Cloud Storage Provider
## 1 Introduction  
The National Institute of Standards and Technology (NIST) defines the cloud as \"a huge pool of easily usable and manageable virtualized resources such as hardware, development platforms and/or services. These resources can be dynamically reconfigured to adjust to a variable load (scale) allowing for an optimum resource utilization. This pool of resources is typically exploited by a pay-per-use model in which guarantees are offered by the Infrastructure Provider by means of customized Service Level Agreements (SLAs)\" [1]. Cloud computing became one of the essential technologies in the last decade. The conventional information technology (IT) setup requires the same location as the data storage device. However, in cloud computing, one can access and update information through the internet from anywhere at any time. Data from the cloud is accessed by a wireless/wired or mobile broadband connection. The common example of cloud computing is webmail, where the service provider maintains the server space and allows access to email service based on their email address and password. Cloud computing provides a variety of services depending on organizations' requirements. Major services are Software as a Service (SAAS), Platform as a Service (PAAS), and Infrastructure as a Service (IAAS). In SAAS cloud computing, the provider ensures availability of both software and internet service. The market for SAAS is end-users. The advantage of SAAS is efficient hardware utilization, with a major drawback being less control. Examples of SAAS are Microsoft Office 365 and Apple iCloud. In PAAS cloudcomputing, the provider maintains an environment for software development. The market for PAAS is developers. Its main advantage is to reduce software concerns, but its major drawback is vendor lock-in. Microsoft Azure and Google App Engine are examples of PAAS. In the IAAS cloud computing structure, a repository and other resources are maintained by the service provider. The market for IAAS is network architects. Its main advantage is full control, and its major drawback is less efficiency. The examples for IAAS include Microsoft Azure and Amazon Web Service (AWS) [2]. Cloud computing has three main types (public, private, and hybrid) with different benefits for each type. The public cloud is a standard cloud computing model in which resources, such as CPU, memory, a repository, and APIs, are available to all users. These services can be public websites like Daraz, or storage space like Dropbox and OneDrive. A private cloud has a restricted environment where services are available through authorization (e.g., government ministry websites). In order to get the flavor of both public and private environments, there is a hybrid cloud. This type is not commonly used owing to some security concerns. Similarly, public users do not easily accept private cloud restrictions. A community cloud is a variant of hybrid cloud that provides services within a community [3]. Figure 1 clearly shows that cloud services are dependent on the user's capability requirement and the openness of the membership. Cloud computing has the following characteristics:  
* On-Request Self-Service  
Cloud computing assists clients to run their resources individually, like server time and network storage, as per their requirements. Usually, most cloud computing users start with limited services, but increase their demand over time. The on-request self-service approach allows end users to request resources at the runtime. When a user requests any resource, this process starts immediately, even though it can be determined by the design and resource availability of the cloud vendor. * Wide Range Network Access  
This means the resources can be accessed from a diverse set of devices such as computers, laptops, mobile phones, tablets, etc., on the network through standard procedures, as shown in Figure 2.  
Resource Sharing  
Vendor's computing resources are shared and stored to serve clients using a multi-tenant model.