Some HPFS features are implemented differently for Windows NT than for OS/2. For example, Windows NT does not support HPFS access control list information or HPFS hot-fixing. (However, these features are available with NTFS.) Also, disk caching and lazy writing are managed by the Windows NT Cache Manager and not the file system.
When you move or copy a file from NTFS to HPFS, any permissions, and alternate streams are lost, and filenames are converted from the Unicode to OEM character set. In addition, the filename becomes case-insensitive.
Windows NT supports HPFS primarily for backwards compatibility for systems that dual-boot OS/2 and Windows NT. NTFS provides all the benefits of HPFS as well as such additional features as security and reliability. Unless a volume must be available to OS/2, the volume should be formatted for NTFS rather than HPFS.