NTFS itself. For example, Windows Vista implemented NTFS symbolic links, Transactional NTFS, partition shrinking, and self-healing. NTFS symbolic links are a new feature in the file system; all the others are new operating system features that make use of NTFS features already in place. Scalability NTFS is optimized for 4 KB clusters, but supports a maximum cluster size of 2MB. (Earlier implementations support up to 64KB) The maximum NTFS volume size that the specification can support is clusters, but not all implementations achieve this theoretical maximum, as discussed below. The maximum NTFS volume size implemented in Windows XP Professional is clusters, partly due to partition table limitations. For example, using 64KB clusters, the maximum size Windows XP NTFS volume is 256TB minus 64KB. Using the default cluster size of 4KB, the maximum NTFS volume size is 16TB minus 4KB. Both of these are vastly higher than the 128GB limit in Windows XP SP1. Because partition tables on master boot record (MBR) disks support only partition sizes up to 2TB, multiple GUID Partition Table (GPT or "dynamic") volumes must be combined to create a single NTFS volume larger than 2TB. Booting from a GPT volume to a Windows environment in a Microsoft supported way requires a system with Unified Extensible Firmware Interface (UEFI) and 64-bit support. The NTFS maximum theoretical limit on the size of individual files is 16EB ( or ) minus 1KB, which totals 18,446,744,073,709,550,592 bytes. With Windows 10 version 1709 and Windows Server 2019, the maximum implemented file size is 8PB minus 2MB or 9,007,199,252,643,840 bytes. Interoperability Windows While the different NTFS versions are for the most part fully forward- and backward-compatible, there are technical considerations for mounting newer NTFS volumes in older versions of Microsoft Windows. This affects dual-booting, and external portable hard drives. For example, attempting to use an NTFS partition with "Previous Versions" (Volume Shadow Copy) on an operating system that does not support it will result in the contents of those previous versions being lost. A Windows command-line utility called convert.exe can convert supporting file systems to NTFS, including HPFS (only on Windows NT 3.1, 3.5, and 3.51), FAT16 and FAT32 (on Windows 2000 and later). FreeBSD FreeBSD 3.2 released in May 1999 included read-only NTFS support written by Semen Ustimenko. This implementation was ported to NetBSD by Christos Zoulas and Jaromir Dolecek and released with NetBSD 1.5 in December 2000. The FreeBSD implementation