## 3 Related Studies  
Big data is data that cannot be stored and administrated on only one computer. Today, to administrate it, computers connected to a distributed file system and working together in a network are used. DFSs are separated into clusters consisting of nodes. Performance, data security, scalability, availability, easy accessibility, robustness, and reliability are the most important features of big data. Big data management problems are solved by using DFS and network infrastructure. DFS-related works began in the 1970s [19]. One of the first studies is The Roe File System and it was developed for replica consistency, easy setup, secure file authorization, and network transparency [20]. LOCUS, developed in 1981, is another DFS that features network transparency, high performance, and high reliability [21]. Network file system (NFS) started to be developed by Sun Microsystems in 1984. This system is the most operated DFS on UNIX. Remote procedure call (RPC) is used for communication [22]. It is designed for enabling Unix file system to function as a 'distributed' system. The virtual file system is used as a layer. Therefore, clients can run different file systems easily and fault tolerance is high in the NFS. File status information is kept, and when an error occurs, the client reports this error status to the server immediately. File replication is not done in NFS, whereas the whole system is replicated [23]. Only the file system is shared on NFS, no printer or modem can be shared. Objects to be shared can be a unit of a directory as well as a file. It is not necessary to set up every application on a local disk in NFS, and there can be shared by using the server. For all that the same computer can be both a server and a client. As a result, NFS reduces data storage costs. The Andrew file system (AFS-1983) and its successor's CODA (1992) and OpenAFS [24] are open sources for distributed file systems. These systems have scalable and larger cluster size. Also, they can reduce server load and cache the whole file. CODA replicates on multiple servers to increase accessibility. Whereas AFS only supports Unix, OpenAFS and CODA support MacOS and Microsoft Windows. In these systems, the same namespace is created for all clients. However, replication is limited, and read-one/write-all (ROWA) schema is used for it [25; 26]. Frangipani was developed as a new distributed file system which is designed as two layers in 1997. The bottom layer consists of virtual disks. These provide storage services. It can be scaled and managed which is done automatically. On the top layer, there are several machines that use the Frangipani file system. These machines run distributed on the shared virtual disk. The Frangipani file system provides consistent and shared access to the same set of files. As the data used in the system grows, more storage space and higher performance hardware elements are needed. If one of the system components does not work, it continues to serve due to its availability. As the system grows, the added components do not make management complicated and thus there is less need for human management [27]. FARSITE (2002) is a serverless file system that runs distributed on a network. It runs distributed on a network of physically unreliable computers. The system is a serverless, distributed file system. It does not require centralized management. Thus, there are not staff costs like a server system. FARSITE is designed to support the file I/O workload of a desktop computer in the university or a large company. It provides reasonable performance using client caching, availability, and accessibility using replication, authentication using encryption, and scalability using namespace delegation. One of the most important design goals of FARSITE is to use the benefits of the Byzantine fault-tolerance [28]. Described in 2006, the CEPH file system is located on a top layer of similar systems that do object storage. This layer separates data and metadata management.