# Research on Blockchain Data Availability and Storage Scalability
## 6 Research on Data Availability and Storage Scalability
### Storage Scalability Metrics  
Data availability and storage redundancy are mutually constrained. With an increase of storage redundancy, the possibility of data single-point failure is reduced, the data response delay is reduced, and the data availability level is increased, but the storage scalability becomes poor; the reduction of storage redundancy improves storage scalability, but the increase in target data acquisition time results in a decrease in the data availability level. We define the storage scalability coefficient as follows:  
Definition of the storage scalability coefficient: It is the ratio of data availability to storage redundancy for scalable storage schemes within a time limit. It is calculated as follows:  
\[S=\frac{A}{R} \tag{9}\]  
where \(S\) represents the storage scalability coefficient, \(A\) represents the level of data availability within the time limit, and \(R\) represents storage redundancy. Storage scalability is directly reflected by the storage scalability coefficient. From an intuitive perspective, the above definition compares data availability and storage redundancy and uses it as a measurement index of storage scalability with strong readability; from a comprehensive perspective, the definition takes into account both data availability and storage redundancy; from the perspective of comparability, the definition can compare and evaluate different scalable storage schemes, therefore providing reference for the selection and optimization of schemes. Therefore, the definition has strong rationality and applicability, and can provide support for the evaluation and optimization of different scalable storage schemes. According to Figure 5 and Table 1, the storage scalability coefficients of SSFL and SSFE can be obtained under different proportions of degraded nodes, as shown in Table 2. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**The Proportion of Degraded Nodes**} & \multicolumn{3}{c}{**Storage Redundancy**} \\ \cline{2-3}  & **SSFL** & **SSFE** \\ \hline
0\% & 1 & 1 \\
10\% & 0.9 & 0.918 \\
20\% & 0.8 & 0.836 \\
30\% & 0.7 & 0.754 \\
40\% & 0.6 & 0.672 \\
50\% & 0.5 & 0.59 \\
60\% & 0.4 & 0.508 \\
70\% & 0.3 & 0.426 \\
80\% & 0.2 & 0.344 \\
90\% & 0.1 & 0.262 \\
100\% & —— & 0.18 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Storage redundancy of SSFL and SSFE. When the proportion of degraded nodes is 0, these two storage schemes are SSF, and the storage scalability coefficients are both equal to 1. When the proportion of SPV nodes is 100%, storage redundancy does not exist, and the storage scalability coefficients also do not exist, it is indicated by \"\(\overline{\text{---}}\)\" in the table. Storage scalability, data availability, and storage redundancy are interrelated and mutually influential. When evaluating any one indicator, it is necessary to comprehensively consider the other two indicators. Although the storage scalability coefficient is not necessarily as high as possible, this value can guide the optimal ratio between the numbers of full nodes and degraded nodes in different scalable storage schemes. Figure 9 shows the changes in the storage scalability coefficient and data availability after normalization in the same coordinate system. As illustrated in Figure 9, in SSFL, the normalized storage scalability coefficient exhibits a trend of initially increasing and then decreasing with the proportion of SPV nodes. The reason for this trend is that when the proportion of SPV nodes is too high, full nodes are required to handle a large volume of data requests, resulting in longer data response times, significantly reduced data availability, and a decreasing trend in the storage scalability coefficient after it reaches its maximum value. The solution to addressing blockchain storage scalability involves minimizing data redundancy and maximizing storage scalability while ensuring a certain level of data availability.