However, the size of the partition has an effect on storage efficiency and it may be appropriate to consider this before partitioning a hard drive, especially a larger drive. Many people decide to partition a hard drive into two or more logical drives to reduce the amount of wasted space on the drive. Hard drives and floppy disks formatted under DOS are divided into sectors during the format process. Each sector can store 512 bytes of data. This is the smallest unit that DOS uses when reading or writing to or from a hard drive or floppy disk.
All data used by a PC is in the form of files.
Although the sector is the smallest unit that DOS deals with when transferring data to and from a drive, the cluster, or allocation unit, is the smallest unit that DOS can use when allocating space to store a file. The size of the allocation unit varies from drive to drive depending on the size of the logical drive. Entries are made in the FAT table to keep track of the location of files on the drive. Each entry can point to only one file, though a file may have any number of entries, depending on the size of the file. Each FAT entry is limited to 16 bits.