Par2 - Revision history

Shakey snake: Redirecting to PAR

2010-04-13T21:46:59Z

Redirecting to PAR

← Older revision		Revision as of 21:46, 13 April 2010
Line 1:		Line 1:
	#REDIRECT [[~~PAR2~~]]		#REDIRECT [[PAR]]

Synthetic Soul: Amended to redirect page. Content now on PAR2

2006-01-03T15:40:41Z

Amended to redirect page. Content now on PAR2

← Older revision		Revision as of 15:40, 3 January 2006
Line 1:		Line 1:
	~~PAR (''parity'') files are created from a source file or files (''recovery set''), and can be used to restore the recovery set if any file becomes corrupted.~~		#REDIRECT [[PAR2]]


	~~=PAR=~~

	PAR files were widespreadly used for Usenet newsgroup multi-part archive files. When posting a file a user could also post PAR files which would allow downloaders to recover any part of the archive by downloading an equal number of PAR files. I.e.: if two parts of the archive were missing or corrupt the downloader would just need to download ''any two'' PAR files and they could successfully recreate the archive.

	~~PAR files are named as follows:~~

	*.PAR
	*.P01
	*.P02
	*.P03
	*etc.

	~~The .PAR file is simply a small (~1KiB) index file for the set, and does not contain any parity data.~~


	~~=PAR2=~~

	PAR2 succeeded PAR; its main benefit being that there is no relationship between the size of the source files and the size of the PAR2 files, ''and'' that undamaged blocks in a corrupt PAR2 file can still be used to recover the recovery set. The [~~http://www.quickpar.org.uk/AboutPAR2.htm QuickPar] website has a good desscription of the main differences between the two formats.~~

	~~PAR2 files are named as follows:~~

	~~'''filename.vol<span style="color:red">nn</span>+<span style="color:purple">mm</span>.~~PAR2~~'''~~

	*'''<span style="color:red">nn</span>''' is the total number of blocks of all preceding files<br>
	*'''<span style="color:purple">mm</span>''' is the number of blocks in this file, and therefore the number of blocks it can repair


	~~=How Does It Work?=~~

	The redundant data in the PAR files is computed using the Reed-Solomon algorithm that allows for recovery of any 'X' real data-blocks for 'X' parity data-blocks present. (data-blocks referring to files ''or'' much smaller virtual slices of files).

	~~For more information read [http://parchive.sourceforge.net/docs/specifications/parity-volume-spec/article-spec.html the full PAR 2.0 specification].~~


	~~=Useful Links=~~

	*[http://parchive.sourceforge.net/ Parchive: Parity Archive Tool] ~~: Home of PAR~~
	*[http://www.quickpar.org.uk/ QuickPar] : A superb PAR/PAR2 GUI
	*[http://www.dvdisaster.com/ dvdisaster] ~~: Although not exactly PAR, dvdisaster uses the Reed-Solomon algorithm to create a correction file for a DVD image~~

Synthetic Soul: Initial page, more info to come...

2006-01-03T13:11:46Z

Initial page, more info to come...

New page

PAR (''parity'') files are created from a source file or files (''recovery set''), and can be used to restore the recovery set if any file becomes corrupted.

=PAR=

PAR files were widespreadly used for Usenet newsgroup multi-part archive files. When posting a file a user could also post PAR files which would allow downloaders to recover any part of the archive by downloading an equal number of PAR files. I.e.: if two parts of the archive were missing or corrupt the downloader would just need to download ''any two'' PAR files and they could successfully recreate the archive.

PAR files are named as follows:

*.PAR
*.P01
*.P02
*.P03
*etc.

The .PAR file is simply a small (~1KiB) index file for the set, and does not contain any parity data.

=PAR2=

PAR2 succeeded PAR; its main benefit being that there is no relationship between the size of the source files and the size of the PAR2 files, ''and'' that undamaged blocks in a corrupt PAR2 file can still be used to recover the recovery set. The [http://www.quickpar.org.uk/AboutPAR2.htm QuickPar] website has a good desscription of the main differences between the two formats.

PAR2 files are named as follows:

'''filename.volnn+mm.PAR2'''

*'''nn''' is the total number of blocks of all preceding files 
*'''mm''' is the number of blocks in this file, and therefore the number of blocks it can repair

=How Does It Work?=

The redundant data in the PAR files is computed using the Reed-Solomon algorithm that allows for recovery of any 'X' real data-blocks for 'X' parity data-blocks present. (data-blocks referring to files ''or'' much smaller virtual slices of files).

For more information read [http://parchive.sourceforge.net/docs/specifications/parity-volume-spec/article-spec.html the full PAR 2.0 specification].

=Useful Links=

*[http://parchive.sourceforge.net/ Parchive: Parity Archive Tool] : Home of PAR
*[http://www.quickpar.org.uk/ QuickPar] : A superb PAR/PAR2 GUI
*[http://www.dvdisaster.com/ dvdisaster] : Although not exactly PAR, dvdisaster uses the Reed-Solomon algorithm to create a correction file for a DVD image