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Old 2005-03-10, 09:09 AM
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Join Date: Oct 2004
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Re: Best way to store all these downloads?

Originally Posted by h_vargas
well, what if the disc corrupts/degrades in a way such that part of the original files are unreadable (let's say 10%) and part of the par2 file(s) are unreadable (again, let's say 10%). wouldn't that mean that there's still come of the disc contents that will be completely unrecoverable? i mean, if some of the par2 file(s) are unreadable plus normal contents archived on the disc are unreadable, it seems as though the par2 system would fail in that scenario... however unlikely that scenario would be.
You are correct, if 20% of the content of the disc becomes corrupted, irregardless of whether or not it's the actual files or the par2 recovery volumes, then you will be unable to recover. Par2 recovery is an "all-or-nothing" affair, and so if you don't have enough good files and recovery volumes to do it, then the only thinkg you're left with are the files that were good from the start. Just to clear something up: it doesn't matter if you lose actual files or par2 recovery volumes, but only the total amount of filesize of the lost files. If you lose more of a % of the total filesize than the redundancy you used when creating the volumes, you're screwed, regardless of which type of file becomes corrupted.

When I make the par2 files, I break up the entire bunch into about 10-12 different files, each containing some of the recovery blocks. This means that if 1 or 2 of them get corrupted, I still have a good deal of chance of complete recovery. In my experience, it's really only 1 or 2 files that can become unreadable on a DVD, and 20% is really overkill in my opinion, which is why I use it. Media is cheap enough that I want to make damn sure I can recover my files. You could go 30% or 40% if you were still afraid of losing more than that, with the obvious ramification being you'll need more space to store the discs. Honestly though, if you store the discs in jewel cases and are gentle with them when using them, they are reliable enough that 20% is big enough.

Originally Posted by h_vargas
just trying to figure out if it's worth my time to use par2 for every archived show i have. i will be re-archving literally thousands of data CDRs (in SHN, FLAC, and a couple of other lossless compressed formats) all to DVDR to have a 2nd backup soon. so i'd like to go about my re-archiving/2nd backup as efficiently as possible.
I would say, if the show is worth keeping, it's worth using par2. Since you're at the front end of a major re-archiving project, do yourself a favor and do it right the first time. Media is very cheap. The chance that some of your shows will be partially corrupted in 5 years is pretty high, but with this method it drops it down to almost zero. Since you don't have a way of knowing ahead of time which shows you're going to lose, in my opinion it's best to be secure, especially given small cost associated with this option.

I would also consider doing things like correcting sector boundaries and adding file tags to all of the files during the transition too, but that's a topic for another thread.
Through the clouds,
Throught the lies,
We'll never see,
What's never been,
At the ending of life and the coming of death,
Pass not through its gates but into the dark.
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