# A Dynamic Decision Support System for Selection of Cloud Storage Provider
## 5 Results and Discussion
### Ranking Validation by Using AHP  
In the first experiment, the cloud storage providers ranking is calculated manually by using AHP and comparing the results with the proposed system. Weights from 1 to 8 are assigned to the parameters according to their importance, '1' represents the minimum whereas '8' indicates the maximum. Maximum weight is assigned to the CPU, Repository and OS owing to their importance. Similarly, the rest of the weights are assigned to the remaining parameters as shown in Table 6.  
In the second step, a pair-wise weight comparison of these parameters is calculated. Parameters with small weights appear with/in that column. The formula used here is R = 1/aij, Table 7 shows a pair-wise comparison of parameters, and data are converted to decimal form. Here, the Trial column indicates a trial version of their cloud services that is provided by some vendors to attract customers. Next, the sum of all columns are calculated after converting to decimal form, as shown in Table 8.  
After calculating the sum of the columns, the next step is to normalize the data. During this process, weights for all parameters are calculated. First of all, each column is divided by its column sum, i.e., _A2/A9_...... _A8/A9_, applying the same procedure for all columns. After that, values in columns are normalized in order to ensure that calculation of the sum for each column will be always equal to 1. Then, the following formula is applied:  
_Priority = Sum of all normalized values row-wise/Total number of columns_  
Multiplying the results by 100 in order to calculate the percentages. Table 9 shows the priority calculations for different parameters in normalized form. After the calculations, the parameter CPU has the maximum priority, and subsequently, remaining parameters. \begin{table}
\begin{tabular}{c c c} \hline \hline
**S No** & **Parameter** & **Weight** \\ \hline
1 & CPU & 8 \\
2 & Repository & 7 \\
3 & OS & 6 \\
4 & Mobile Access & 5 \\
5 & Sync & 4 \\
6 & Sharing & 3 \\
7 & Free Storage & 2 \\
8 & Trial & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Parameters with their Weights. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Parameters** & **CPU** & **Rep** & **OS** & **Mobile Access** & **Sync** & **Sharing** & **Free Storage** & **Trial** \\ \hline
**CPU** & 1 & 2 & 5 & 5 & 6 & 6 & 8 & 8 \\
**Rep** & 1/2 & 1 & 5 & 5 & 6 & 6 & 8 & 8 \\
**OS** & 1/5 & 1/5 & 1 & 2 & 5 & 5 & 5 & 9 \\
**Mobile** & 1/5 & 1/5 & 1/2 & 1 & 2 & 2 & 5 & 5 \\
**Access** & 1/6 & 1/6 & 1/5 & 1/2 & 1 & 2 & 2 & 2 \\
**Sync** & 1/6 & 1/6 & 1/5 & 1/2 & 1/2 & 1 & 5 & 5 \\
**Sharing** & 1/6 & 1/6 & 1/5 & 1/2 & 1/2 & 1 & 5 & 5 \\
**Free Storage** & 1/8 & 1/8 & 1/5 & 1/5 & 1/2 & 1/5 & 1 & 2 \\
**Trial** & 1/8 & 1/8 & 1/8 & 1/5 & 1/2 & 1/5 & 1/2 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Parameter Paired Comparisons. The rank of each parameter is calculated, and a pair-wise comparison is performed later. The max value for CPU cores has a high weight and vice versa as shown in Table 10. The same above process is repeated to calculate weights for the remaining parameters. Table 10 shows column-wise sums, whereas Table 11 shows the priority with in the CPU parameter (i.e., the max CPU value is 24 cores and has max priority). Next, the repository parameter is compared with its maximum and minimum values. The logic is the same; maximum weight is given to maximum storage, and vice versa. Table 12 shows the weights and a comparison of the column-wise sum of the repository parameter. The priority for the Repository is calculated by using the AHP as shown in Table 13. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**CPU** & **24 Cores** & **1 Core** & **4 Cores** & **8 Cores** \\ \hline
**24 Cores** & 1.00 & 7.00 & 5.00 & 3.00 \\
**1 Core** & 0.14 & 1.00 & 0.33 & 0.20 \\
**4 Core** & 0.20 & 3.00 & 1.00 & 0.25 \\
**8 Core** & 0.33 & 5.00 & 4.00 & 1.00 \\ \(\tilde{\Sigma}\) & 1.68 & 16.00 & 10.33 & 4.45 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Column-wise sums of the CPU Parameter.