PAR2 File Creation Options

Hey everyone,

For those of you that are creating par2 files in order to add some redundancy to your dvd backups, what block size/block count are you using? I'm currently trying to create par2 files on a dvd sized image - 20% with 20% par2 redundancy and the process is slow (Were talking a few hours). Anyway, just wondering if anybody knows anyway to speed the process up a bit.

Thanks.

[wazoo2u]

I'd try creating the archive as a RAR set, and then make PAR's for those files which are much smaller. If you get a disk read error, it's much easier to recreate a few bad RAR's from your PAR set than to reconstruct a 1 gig .VOB.

I'd think that a 5% redundancy would suffice.

Make sense ?

[RainDawg]

Originally Posted by quijobe

Hey everyone,

For those of you that are creating par2 files in order to add some redundancy to your dvd backups, what block size/block count are you using? I'm currently trying to create par2 files on a dvd sized image - 20% with 20% par2 redundancy and the process is slow (Were talking a few hours). Anyway, just wondering if anybody knows anyway to speed the process up a bit.

Thanks.

It does take a few hours to create the resconstruct volumes for a single DVDs worth of files. When you start dragging files into QuickPar, it will automatically adjust the block size to the most efficient value (efficiency is displayed at the bottom), meaning that you'll get the most redundancy in the smallest amount of filesize. The only option you really need to tweak is you can uncheck the one that says "restrict block size to multiples of usenet article size", unless you're planning on posting them to a usenet site.

You do not need to .rar these. Back in the days of par1, dealing with files of varying sizes was very poor, and so people were forced to make multivolume .rar files to make everything the same size. This is no longer needed.

But yes, several hours to create the volume is expected, and normal.

What type of machine are you running quickpar on and how much time does it usually take you to create the volumes? I'm interested to see how much of a difference I'll see if I upgrade the machine that I've been using the par2 tools on.

[wazoo2u]

Originally Posted by RainDawg

You do not need to .rar these. Back in the days of par1, dealing with files of varying sizes was very poor, and so people were forced to make multivolume .rar files to make everything the same size. This is no longer needed.

Either I'm missing something here, or you misunderstood my point. My premise is that PAR files (of any flavor) need to be AT LEAST as large as the data set they are replacing. PAR1 had a disadvantage because you needed PAR files that were AT LEAST the size of the biggest file in the set. PAR2 requires that you only need to replace the data that is missing.

Unfortunately, If you have a bad DVD, and your reader cannot extract a certain file AT ALL, then you will need enough PAR blocks to re-create the entire file. Since .VOB files are generally over 1 gigabyte, then you are instantly forcing yourself to create (assuming 4+gig DVD total) a 25% redundancy, just to recreate a missing VOB. If we were downloading this from Usenet, we could assemble a partial file, and possibly only require a few PAR2 blocks, but in a "bad sector read" scenario, we MIGHT need much more. I'll agree that a damaged VOB MIGHT be partially recoverable using programs like CDRoller or CDExtract, in which case you might need less blocks.

So the reason I recommended RAR archives was an attempt to minimize the potential data loss if there was damaged and unrecoverable files. Given the fact that you would need to create far less PAR2 blocks, the creation of the RAR set shouldn't be a huge difference in the time it would take to create the total archive (I think). BTW, I do NONE of this. I simply burn a backup DVD and hope for the best. If I lose it, it's a rock and roll show... not a member of my family... (thank goodness).

It makes sense to me, now tell me why I'm wrong

[RainDawg]

I think we're both right, but talking about different things. I am not making reference to video DVDs at all, but rather Data DVD backsups of FLAC/SHN files. Typically, these files are much smaller so 20% redundancy is more than enough should a handful of those files become corrupt or unreadable. I have not started making backups of video DVDs in this manner yet, though at some point in the fuiture I'll have to figure what the best way is.

In that case, yes, .rar backups would be prudent but even moreso is your second suggestion: using CD roller and hoping that the recovery volumes are able to use the rest of the files (save for the corrupted block), in which case 2-3% redundancy would be more than enough to recover a flawed disc, even if all of the .VOBs were missing parts. Of course, this relies on a bit of a leap of faith in that I am not sure that taking one small chunck from a huge file and then running it through just a few recovery volumes will fix it, and I've not had the time to run any tests. Before I do anything with par2 and video DVDs, some testing would have to be done; that's a future project for me.

So yes, you're right, but we were thinking of different things. For Data DVDs, there's no need to do anything to the files you're protecting since they are small enough that a few can be trashed completely and a full recovery is still quite probable.

[RainDawg]

Originally Posted by quijobe

What type of machine are you running quickpar on and how much time does it usually take you to create the volumes? I'm interested to see how much of a difference I'll see if I upgrade the machine that I've been using the par2 tools on.

I have a fairly high-end machine (though a bit weak on RAM) with an Athlon 3200+ running at 400 MHz bus speed. To make 1 DVDs worth of backup volumes, assuming no other activity on the computer, it will take a little over an hour. I usually setup 3-4 DVDs and let them run at the same time overnight, and when I get up the discs are ready to burn. It's probably taking it's toll on my hard drives, but that's why I obsessively back things up with par2....in the event of an HD crash, I don't want to lose much.

[wazoo2u]

Originally Posted by RainDawg

I think we're both right, but talking about different things. I am not making reference to video DVDs at all, but rather Data DVD backsups of FLAC/SHN files.
<snip>
So yes, you're right, but we were thinking of different things. For Data DVDs, there's no need to do anything to the files you're protecting since they are small enough that a few can be trashed completely and a full recovery is still quite probable.

I thought we were talking about backing up Video DVD's. Of course, the methods for Data DVD's would be different, since individual file sizes are generally much smaller. The original post said

I'm currently trying to create par2 files on a dvd sized image - 20% with 20% par2 redundancy and the process is slow

so of course, my method was to break the image down to smaller and more manageable/recoverable pieces. Sorry for the confusion.

Sometimes we take too much for granted, I guess.

[Beleaguered]

I understand what you are saying about using smaller rar's, but I think it's redundant when you consider that data on cds and dvds are stored in a given sector size (we all know about sbe's): 2048 bytes for cds and 2352 for dvds. Thus, you really only need to fix the bad sectors in a file, not the whole file regardless of whether it's a rar, flac, or vob file.

I use the following process when doing dvd backups... Make a dvd image (write it to the hard drive, not the dvd yet). Create a par2 recovery file of that image using some multiple of the dvd sector size. Burn the image to dvd. If the dvd goes bad, you can write the disk image back to disk ignoring the bad sectors (using IsoBuster or a similar program) and repair it with the par2 files.

I admit to not having actually tested the recovery process. I should scratch up a disk and restore the image.

My 2¢

[wazoo2u]

Originally Posted by Beleaguered

I use the following process when doing dvd backups... Make a dvd image (write it to the hard drive, not the dvd yet). Create a par2 recovery file of that image using some multiple of the dvd sector size. Burn the image to dvd. If the dvd goes bad, you can write the disk image back to disk ignoring the bad sectors (using IsoBuster or a similar program) and repair it with the par2 files.

I admit to not having actually tested the recovery process. I should scratch up a disk and restore the image.

My 2¢

You should experiment with your recovery method, but it does sound good in theory. My gut feeling is that sector recovery is a chancy proposition in general. If you use this method (PAR files based on image creation), then I really don't know if I can offer any "timesaving" techniques, other than a fast bus and SATA drives. BTW, IsoBuster has limited functionality in it's "freeware mode". I don't know if "ignore bad sector mode" is included in the free version, but I hate to recommend tools that people need to pay for, if there are free alternatives.

You should let us know about recovery results, and note the time it takes both to create the image, create the PAR's, extract the image and then to repair... my guess is "quite a while"

Thanks for all of the great responses. My original post was in reference to making backups of flac files on dvds, not dvd videos. Sorry for the confusion.

After playing with par2 for a while, I've decided that I will take all of the files that I want to burn and place them in a directory somewhere, run par2create with redundancy set at 20%, number of files set at 10 and block size set somewhere about 1MB. After the paring is done, I'll burn the dvd and then verify the files on the dvd as well as the par2 information.

Let me know if you see any holes in my plan.

Thanks.

[wazoo2u]

Just playing devil's advocate here cause I don't really know the answer.

Why would you set the block size that large ? Typical PAR blocks for Usenet posting are made in the same size as the posting line count. Why bigger ?? As was mentioned in the thread, would you make PAR blocks to equal the default sector size ?

[wazoo2u]

Originally Posted by wazoo2u

Just playing devil's advocate here cause I don't really know the answer.

Why would you set the block size that large ? Typical PAR blocks for Usenet posting are made in the same size as the posting line count. Why bigger ?? As was mentioned in the thread, would you make PAR blocks to equal the default sector size ?

I should have read Stephen's post above a bit closer. I see that QuickPar handles block sizes automatically. Disregard the above lamebrained questions

[Beleaguered]

If you have doubts about your method, I suggest you check the QuickPar forum where the par2 creator is:
http://www.quickpar.org.uk/forum/

There's also been prior conversation on this at HA, for example:
http://www.hydrogenaudio.org/forums/...showtopic=9236
http://www.hydrogenaudio.org/forums/...howtopic=18456

Thanks for the links. The second one was very informative.