# Performance Analysis of Storage Systems in Edge Computing Infrastructures
## 2 Related Work  
The Internet of Things and WEB 4.0 are quickly becoming more dominant in more and more domains and daily life or industrial applications. This gives rise to a series of new challenges and problems that researchers are actively trying to tackle, both in the cloud [17] and in the edge [18; 19]. One of the major problems that falls in this category is the minimization of data latency and network overload in fog or edge networks [20]. One of the most common solutions for this problem is the development of edge storage methodologies in order to move all or part of the necessary data and their processing to the edge, near the edge devices that use them. Edge storage services are actively focusing on decentralization and resource efficiency due to the nature of the edge networks and the devices that are taking part in them. These two main goals are driving the current research in the field. A plethora of traditional technologies in storage are being adapted in order to fit these two requirements, such as the blockchain and block storage technologies. Blockchain [21] is the well-known technology that came into existence in order to support Bitcoin, but since then, blockchain has developed a \"life\" of its own, being used in a great deal of other use cases and domains. Blockchain works by creating a central repository of transactions in the form of chained exchanges. Each of these exchanges must be validated by a number of peers in order to be registered in this central repository and be considered a valid transaction. When being applied in edge storage, blockchain has two major flaws: it needs heavy computational power to perform the transaction validations and it requires a centralized database in order to store the chain of transactions [22]. These two characteristics are causing direct conflict with the decentralization and low resource demand requirements of edge storage services. That is the reason that many researchers are trying to combine it with other technologies, such as peer-to-peer networks, limiting or even completely countering these flaws. Peer-to-peer (P2P) networks are a form of file storage and file sharing technology that is fully decentralized. These types of networks are using a set of protocols that ensure the safe and secure communication between the interconnected devices, called \"peers\" [23]. These protocols are usually lightweight, adding only minimal overheads to the actual data that peers are exchanging between themselves [24]. Modern peer-to-peer networks are using distributed hash tables (DHT) in order to enhance their functionality and security, some of them even integrating encryption algorithms in order to protect their data from a wider set of possible attacks [25]. The problem with these networks is in the integrity, immutability, and reliability because they provide no adequate security controls over these factors [26]. This limitation is forcing researchers to combine them with other, more secure technologies, such as blockchain, which provide the missing controls. The literature is actively trying to find a balance between the available frameworks by comparing their throughput, resource efficiency, and limitations, either on their own or when combined with each other. Blockchain and P2P networks are widely used for this purpose because peer-to-peer networks seem the ideal candidate for edge storage solutions, if the drawbacks already mentioned can be tackled. In relevant experiments, the interaction between these two frameworks seems to provide an efficient solution to the edge storage problem because blockchain can cover almost all of the weaknesses that P2P networks possess without adding much overhead, both in read/write operations, the throughput, and the network traffic [22; 27; 28; 29]. The only drawback is that blockchain mechanisms require more redundancy than P2P, which requires more available disk space in the edge clusters that host these solutions, placing limitations on the network architecture options for IoT and fog networks.