HPFS
Encyclopedia : H : HP : HPF : HPFS
| HPFS | |
|---|---|
| Developer | Microsoft |
| Full name | High Performance File System |
| Introduced | November 1989 (OS/2 1.2) |
| Partition identifier | 0x07 (MBR) |
| Structures | |
| Directory contents | B+ tree |
| File allocation | B+ tree |
| Bad blocks | B+ tree |
| Limits | |
| Max file size | 2 GiB |
| Max number of files | Unlimited |
| Max filename size | 255 characters |
| Max volume size | 2 TiB |
| Allowed characters in filenames | Double-byte from 0x0020 to 0xFFFF |
| Features | |
| Dates recorded | Access, Creation, Modified |
| Date range | Unknown |
| Forks | Yes |
| Attributes | Read-only, hidden, system, archive |
| File system permissions | Yes (only in HPFS386) |
| Transparent compression | No |
| Transparent encryption | No |
| Supported operating systems | |
HPFS or High Performance File System, is a file system created specifically for the OS/2 operating system to improve upon the limitations of the FAT file system. It was written by Gordon Letwin and others at Microsoft and added to OS/2 version 1.2, at that time still a joint undertaking of Microsoft and IBM.
Among its improvements are
- support for mixed case file names, in different code pages;
- support for long file names (256 characters as opposed to FAT's 11 characters);
- more efficient use of disk space (files are not stored using multiple-sector clusters but on a per-sector basis);
- an internal architecture that keeps related items close to each other on the disk volume;
- less fragmentation of data;
- extent-based space allocation;
- separate datestamps for last modification, last access, and creation (as opposed to FAT's one last modification datestamp);
- a b-tree structure for directories; and
- root directory located at the mid-point, rather than beginning of the disk, for faster average access.
IBM offers two kind of IFS drivers for this file system: the standard one with a cache limited to 2 MiB, and HPFS386 provided with the server versions of OS/2. HPFS386's cache is limited by the available memory. It's highly tunable by experienced administrators. Thus, HPFS386 is faster, but IBM is required to pay Microsoft for each copy sold.
Because of the Microsoft dependence and the longer disk check times after a crash, IBM ported the journaling file system JFS to OS/2 as a substitute.
There are also third-party drivers for DOS and Linux and official ones for Windows NT.
See also
- Comparison of file systems
Further reading
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.