View source for Professional File System

{{Short description|Improved file system for AmgaOS}}
[[File:pfs3.png|right]]
{{Infobox Filesystem
| name = PFS
| full_name = Professional File System
| developer = Michiel Pelt
| introduction_os = [[AmigaOS]]
| introduction_date = {{Start date and age|1995}}
| partition_id = 'PFS\1', 'muAF', 'AFS\1' ([[Amiga Rigid Disk Block|RDB]])
| directory_struct = 
| file_struct = 
| bad_blocks_struct = 
| max_filename_size = 107 characters
| max_files_no = 
| max_volume_size = 104 [[gigabyte|GB]] (101 [[gibibyte|GiB]])
| max_file_size = 
| filename_character_set = All bytes except NULL, ':' and '/'
| dates_recorded = modification (mtime)
| date_range = January 1, 1978 - 2157
| date_resolution = 1/50s
| forks_streams = 
| attributes = filenote
| file_system_permissions = Amiga permissions, [[multiuser]] permissions
| compression = No
| encryption = No (provided at the block device level)
| single_instance_storage = No
| OS = [[AmigaOS]], [[MorphOS]], [[AROS]]
}}

The '''Professional File System''' is a [[filesystem]] originally developed commercially for the [[Amiga]],<ref>{{cite magazine |date=January 1995|title=Trois nouveaux gestionnaires de disque venant du DP, FFS versus PFS: un combat gagné d'avance?|language=French|magazine=AmigaNews|publisher=NewsEdition|issn=1164-1746|issue=75|pages=76}}</ref> 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.<ref name="EAL">{{cite journal|last=Favini |first=Andrea |title=Professional File System 3 |url=http://www.amigalife.info/inediti/inediti2-prove2.html |journal=Enigma Amiga Life |location=Italy |issue=122 |access-date=3 October 2015 |url-status=unfit |archiveurl=https://web.archive.org/web/20020529194129/http://www.amigalife.info/inediti/inediti2-prove2.html |archivedate=May 29, 2002 }}</ref><ref>{{cite magazine |last=Drummond|first=Richard|date=Christmas 1999 |title=Professional File System 3|magazine=Amiga Format |publisher=Future Publishing|issn=0957-4867|issue=131|pages=48–49}}</ref> It also features multi-user abilities like the older [[MuFS]].<ref name="EAL" />

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{{cn|date=October 2015}} filesystem.<ref name="EAL" />

It was the first{{cn|date=October 2015}} filesystem to introduce the concept of the [[Recycle bin (computing)|Recycle Bin]] natively at filesystem-level to the Amiga, holding the last few deleted files in a hidden directory on the disk root.<ref name="EAL" />

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

==See also==
{{Portal|Amiga}}
* [[Amiga Old File System]]
* [[Amiga Fast File System]]
* [[Smart File System]]
* [[File system]]
* [[List of file systems]]

==References==
{{Reflist}}

==External links==
*[https://github.com/tonioni/pfs3aio Official repository]
*[https://aminet.net/package/disk/misc/pfs3aio PFS3 All-In-One]

{{AmigaOS}}
{{MorphOS}}
{{File systems}}

[[Category:Disk file systems]]
[[Category:Amiga software]]
[[Category:AmigaOS]]
[[Category:MorphOS software]]
[[Category:AROS software]]
[[Category:Free system software]]