PAR2 Files

aybesea

aybesea

1
I'm very familiar with PAR files and their use. I've been using these for well over a year and find them invaluable. I believe that FSRaid is easily the best of the PAR file programs.

Recently I have come across PAR2 files. I understand that they are for use in restoring bits of a file rather than the entire file... useful for the Usenet, for example.

FSRaid does not yet handle PAR2 (at least that I can tell). For any of you with PAR2 experience, what is the best available client? Any tips?
 
VIPER_1069

VIPER_1069

1
bits of a file !? :confused: why would you only want to partly repair a file and not replace it with a totally recreated copy of the broken/missing file !? of say a spanned image or exe !? seems a little odd !? sure it would save time downloading as many par's but i dont see it being as reliable to part repair a part broken file !? :confused:

ive had experience with lots of files with pars and successfully restored missing or damaged files using FSraid !? never heard of par2 ?!
 
aybesea

aybesea

1
Viper, think of it like this. I download 29 parts of a 30 part post from the Usenet. I'm not talking 29 rar files, but rather 29 pieces of one rar file. Then I can use PAR2 to fix the 30th piece and make me a usable rar file.

So, if the total download was 100 rar files, and the problems are with 3 of them. If I have all but 1 good piece of each of the bad rars, then I only need enough info to fix 3 pieces, not 3 whole rars. Get it?

Anyway, it is brand new stuff and I am trying to get used to it. But I need a good client for it. I assume that FSRaid will be updated sooner or later, but right now the only thing I know of is something called QuickPAR that I've not used before.
 
VIPER_1069

VIPER_1069

1
yeah i know what ya mean image files usually arrive in 50+ spanned rars as you know :) currently with par's usually with so many percentage par files !? whatever the span creator deems sufficient to cover that span ?! if you have a corrupt file you then use the pars to replace the files in its entire form !? :)

i think i get the general idea that you only need a few par2 files to repair the part of a file thats corrupt and only the corrupt part !? say it was a 20mb file and 18mb was ok and 2 mb was corrupt the par2 file repairs the 2mb making the file 20mb instead of replacing the whole 20mb !? i think thats wat yer saying here !? gettin confused with my own rant here lol :)


sounds like a interesting idea but logic tells me its not much better than what we have with par files !? if you have missing files then you will still have to have a 20mb par2 file to replace this missing file !? so defeats that object of downloading less pars !? does it not !?
 
VIPER_1069

VIPER_1069

1
@ blane no kidding on the complicated part !? <img src="http://smilies.sofrayt.com/%5E/_950/upset.gif" width="20" height="20">
???

but this part
But you will need to download a greater quantity of PAR2 files than you would otherwise and repair will take considerably longer as a result. Reconstructing a whole file with PAR2 will always take longer than PAR1 would.
Click to expand...
seems pointless for broadband/adsl/cable users as they can just download the original type PAR files and replace a whole file :) with a PAR2 file to reconstruct a whole missing file it appears you would still have to do the same thing !? download a whole par2 file thats the same size !?

sure downloading a small file to repair an already broken file seems in practice a good idea but i would much rather have a whole new file created that i know is valid !?

anyhow unless it takes off big like par files did then i dont think i will be rushing to use it !? :)
 
L

LTR12101B

1
I've NEVER been able to understand MULTIPLE recovery.

Now I used to use a system with a tape backup that used "redundancy groups" - aka "XOR groups" where an extra block, the "exclusive Or" product of the data blocks in the group (default 10) can be used to recover ONE missing missing block by XOR-ing out the ones you do have to leave the missing one.

How you go further than that and still stay at 1:1 ratio is beyond me.
 
M

Markbot

1
I download about 5GB every day from alt.binaries news servers. In the last few weeks, PAR2 files are becoming as prevalent as PAR files. I downloaded the software to use them but could not intuitively figure out how to use it like FSRAID.

I'm even seeing PAR2 files being posted for a series of shn files and not rar's.
 
aybesea

aybesea

1
Exactly!

I'm not ready to pass judgement on PAR2, since I haven't really figured it out yet. But it looks like I won't have much choice, since many of the groups are already using PAR2 (and not PAR).

Again, QuickPAR seems to support this. But I haven't seen anything else. And, as you guys noted, QuickPAR (and its instructions are less than intuitive).

Any other info would be appreciated. Let's keep this thread updated as we gain collective experience!
 
aybesea

aybesea

1
Well, at this point I can tell you three things...

1) PAR2 files DO work... I was able to recover partial files correctly. That part is cool!

2) PAR2 recovery is VERY slow compared to PAR recovery.

3) QuickPAR, while a decent app, is nowhere near the app that FSRaid has become.

If folks are going to continue to use PAR2, the algorithm needs some serious optimization for speed purposes. And either FSRaid needs to get onboard, or someone needs to build a killer app quickly.
 
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