File Systems

The on-disk format for NTFS has been enhanced in Windows 2000 to enable new functionality. The upgrade to the new version of NTFS occurs when Windows 2000 mounts an existing, locally installed NTFS volume. The upgrade is automatic and the conversion time is independent of volume size. FAT16 and FAT32 volumes can be converted to NTFS format at any time by using the Convert.exe tool.



The location of the MFT is different on volumes that have been converted from previous version of NTFS, so volume performance might not be as good on volumes converted from Windows NT.

You can also upgrade FAT16 and FAT32 volumes to NTFS by using the Convert tool. The conversion of a disk volume from FAT to NTFS requires a sufficient amount of available free disk space to build the NTFS disk structures. For more information about the Convert tool, see Convert: Converts a Volume from FAT to NTFS later in this chapter. For additional information about using Convert to convert a volume to NTFS, see the Knowledge Base link on the Web Resource page at . Search using the keywords Convert, NTFS, and winnt.

Conversion Issues for NTFS and FAT Volumes

FAT and NTFS use very different on-disk structures to represent the allocation of space for files. These structures are often referred to as metadata or file system overhead. Another kind of overhead associated with FAT and NTFS is related to the fact that both file systems allocate disk space in clusters of a fixed size. The exact size of these clusters is determined at format time, and are dependent on the size of the volume. See Table 17.2 for the default cluster sizes of each file system per volume size range.

Like FAT, NTFS has a certain amount of fixed-size overhead and a certain amount of per-file overhead. To support the advanced features of NTFS, such as recoverability, security, and support for very large volumes, the NTFS metadata overhead is somewhat larger than the FAT metadata overhead. However, because NTFS clusters are smaller than FAT clusters for the same size volume, you can store more data on an NTFS volume as on a FAT volume of identical size, even without using NTFS file compression.

Convert builds the NTFS metadata by using space that FAT considers free space. Thus, if the conversion fails, the FAT representation of the user files is still valid.