Every file in NTFS is described by one or more records in an array stored in a
special file called the master file table (MFT). The size of a record is determined
when the file system is created; it ranges from 1 to 4 KB. Small attributes
are stored in the MFT record itself and are called resident attributes. Large
attributes, such as the unnamed bulk data, are called nonresident attributes
and are stored in one or more contiguous extents on the disk. A pointer to
each extent is stored in the MFT record. For a small file, even the data attribute
may fit inside the MFT record. If a file has many attributes—or if it is highly
fragmented, so that many pointers are needed to point to all the fragments
—one record in the MFT might not be large enough. In this case, the file is
described by a record called the base file record, which contains pointers to
overflow records that hold the additional pointers and attributes.