Professional File System

PFS
Developer(s)Michiel Pelt
Full nameProfessional File System
Introduced1995; 31 years ago (1995) with AmigaOS
Partition IDs'PFS\1', 'muAF', 'AFS\1' (RDB)
Limits
Max volume size104 GB (101 GiB)
Max filename length107 characters
Allowed filename
characters		All bytes except NULL, ':' and '/'
Features
Dates recordedmodification (mtime)
Date rangeJanuary 1, 1978 - 2157
Date resolution1/50s
Attributesfilenote
File system
permissions		Amiga permissions, multiuser permissions
Transparent
compression		No
Transparent
encryption		No (provided at the block device level)
Data deduplicationNo
Other
Supported
operating systems		AmigaOS, MorphOS, AROS

The Professional File System is a filesystem originally developed commercially for the Amiga,[1] now distributed on Aminet with a 4-clause BSD license. It is a compatible successor of AmiFileSafe (AFS), with an emphasis on added reliability and speed compared to standard Amiga filesystems.[2][3] It also features multi-user abilities like the older MuFS.[2]

The device is split into two main areas. At the beginning of the device is the metadata section, which consists of a root block, and a generic array of blocks that can be allocated to store metadata. The rest of the device is another contiguous generic array of blocks that can be allocated to store data. The metadata section usually uses a few percent of the device, depending on the size of the device.

The metadata is stored as a tree of single blocks in the metadata section. The entire directory structure is recorded in the metadata, so the data section purely contains data from files. The metadata describes the location of data in files with extents of blocks, which makes the metadata quite compact.

When a metadata update occurs, the system looks at the block containing the metadata to be changed, and copies it to a newly allocated block from the metadata section, with the change made, then it recursively changes the metadata in the block that points to that block in the same way. This way, eventually the root block needs to be changed, which causes the atomic metadata update.

The filesystem is reasonably good at keeping files unfragmented, although there is a defragmentation tool available which will work on an online[citation needed] filesystem.[2]

It was the first[citation needed] filesystem to introduce the concept of the Recycle Bin natively at filesystem-level to the Amiga, holding the last few deleted files in a hidden directory on the disk root.[2]

PFS version 5.3 was developed in C and a small portion of assembly code by Michiel Pelt.

See also

References

  1. ^ "Trois nouveaux gestionnaires de disque venant du DP, FFS versus PFS: un combat gagné d'avance?". AmigaNews (in French). No. 75. NewsEdition. January 1995. p. 76. ISSN 1164-1746.
  2. ^ a b c d Favini, Andrea. "Professional File System 3". Enigma Amiga Life (122). Italy. Archived from the original on May 29, 2002. Retrieved 3 October 2015.
  3. ^ Drummond, Richard (Christmas 1999). "Professional File System 3". Amiga Format. No. 131. Future Publishing. pp. 48–49. ISSN 0957-4867.

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