In computing, a file system or filesystem, controls how data is stored and retrieved. Without a file system, information placed in a storage medium would be one large body of data with no way to tell where one piece of information stops and the next begins. By separating the data into pieces and giving each piece a name, the information is easily isolated and identified. Taking its name from the way paper-based information systems are named, each group of data is called a "file". The structure and logic rules used to manage the groups of information and their names is called a "file system".
Cluster size Edit
Higher cluster (allocation unit) sizes could improve performance, as the file system driver has to handle fewer clusters over the partition.
However, in combination to a high number of small files, they waste more space to cluster overhead (unused reserved space). More modern file systems such as NTFS and ext4 handle small cluster sizes more efficiently than earlier ones such as FAT32/16/12, with less performance loss and fragmentation, but are compatible on fewer devices and operating systems.