A storage disk typically is composed of physical blocks of identical size called sectors; size of a sector is usually 512 bytes or in multiples, depending on type and capacity of storage. A sector is the minimal unit of I/O on the disk. When a disk is presented to the filesystem for management, it perceives storage area as an array of blocks of fixed size, where each block is identical to a sector or multiples of sector size. Typical default block size is 1024 bytes and can vary as per disk capacity and filesystem type. Block size is considered the minimal unit of I/O by a filesystem:
