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Topic: Backing up audio files, using Quickpar for verification (Read 6550 times) previous topic - next topic
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Backing up audio files, using Quickpar for verification

I am going to be backing up all of the audio files on my PC.  I want to use Quickpar for all of these files, for verification and recovery purposes.

I plan on using 10% redundancy for all of my FLAC files, which are essentially all live shows from livedownloads.com and irreplaceable.  For all of my .mp3s, which I have actual CDs of, I plan on only using 5% redundancy.

I plan on doing this all using sweep.exe as outlined here: http://www.angelfire.com/magic2/hq-audio/par2-guide.htm


I was wondering if anyone could give me some input on what a good value to use for the block size would be.  I am not really sure what to choose.  Am I making this decision based SOLELY on how long it will take my PC to complete these tasks?  Or are there other things to consider?

Backing up audio files, using Quickpar for verification

Reply #1 –
What medium are you backing the files onto? If it is removable hard drive then I personally wouldn't bother with any par or similar approach. I would simply make sure  that I had at least two copies of everything, on separate hard drives, in different locations. Then periodically run a disc check on both drives.

Backing up audio files, using Quickpar for verification

Reply #2 –
I would prefer to have par2 verification just becauase the drive I will have the backup on now may not be the drive I have backups on in the future.  It would be nice to have a way to make sure nothing has become corrupted during any transfer process, ya know. Or if I ever need to burn to DVD-Rs for any reason.

Backing up audio files, using Quickpar for verification

Reply #3 –
The smaller the block size, the longer it takes to create the PAR2 files.

For FLAC music files, they will usually be 25 to 40 MB each in size.  Thus, I would recommend a block size of 2 MB (2,097,152 bytes).  A block size of 1/16 the average filesize of the original files works best for me.

Then make sure that, with the ~10% redundancy you desired, the number of recovery files is a whole divisor of the number of recovery blocks.  An 8:1 ratio often works best for me.  For example, 100 recovery files, and 800 recovery blocks.  Jiggle the number of recovery blocks and the recovery files until you match an 8:1 ratio.  Therefore, you will get a redundancy percentage of say, 10.58%, or 10.32%, or whatever.

I also make sure that all recovery files are the same size.  It actually makes recovery easier this way, should one or more of the recovery files be corrupt.  You can just delete them, and having enough source files present, can still recover, as even the corrupted recovery file can be recovered.  If you leave the recovery file size as one of the Variable settings, then your recovery ability depends on the size of the corrupt recovery file.  The larger the corrupt recovery file, the less can be recovered.




Backing up audio files, using Quickpar for verification

Reply #4 –
I was hoping to do one recovery file per album.

Backing up audio files, using Quickpar for verification

Reply #5 –
Quote from: ALiENscApE on
I was hoping to do one recovery file per album.


I'm making an assumption here, but there's a chance that you're thinking about doing par2 for each album separately. While that certainly is the cleaner option from an organizational standpoint, the nature of parity means that you're better off running par2 against all your music at once.

Using your example of 10% redundancy for each album, if out of 50 albums, you only lose 50% of one to disk corruption, you lose that album.
If you've run parity on the 50 albums in your collection together, 50% of one album comes to ~1%, well within the 10% redundancy.

Backing up audio files, using Quickpar for verification

Reply #6 –
Quote from: jackhole on
I'm making an assumption here, but there's a chance that you're thinking about doing par2 for each album separately. While that certainly is the cleaner option from an organizational standpoint, the nature of parity means that you're better off running par2 against all your music at once.

Using your example of 10% redundancy for each album, if out of 50 albums, you only lose 50% of one to disk corruption, you lose that album.
If you've run parity on the 50 albums in your collection together, 50% of one album comes to ~1%, well within the 10% redundancy.


I see what your saying.  Does this mean making an entire new set of par2s everytime I backup?

Backing up audio files, using Quickpar for verification

Reply #7 –
Quote from: ALiENscApE on
Does this mean making an entire new set of par2s everytime I backup?


Yes, you'd need to generate a new set of par2s every time you altered your collection. You could split your collection into segments of the largest size you'd want to recalculate par2 values for of course.

It is for this reason (and the inexpensiveness of hard drives) people tend to not use par2 for backups anymore and just use redundant copies that they verify with MD5 or SHA1 checksums, as pdq suggested. As I'm sure you've noticed most of the tools haven't been touched for a while.

Backing up audio files, using Quickpar for verification

Reply #8 –
So you're suggesting just creating MD5 checksums for each album, then copying all my albums with said checksums onto said backup drive, correct? Then if corruption is encountered just restoring from the other drive?

What if I decide to change my Id3 tags after checksums have been created?

Backing up audio files, using Quickpar for verification

Reply #9 –
Quote from: ALiENscApE on
So you're suggesting just creating MD5 checksums for each album, then copying all my albums with said checksums onto said backup drive, correct? Then if corruption is encountered just restoring from the other drive?

What if I decide to change my Id3 tags after checksums have been created?


Then you'd have to recalculate those checksums and resync your backups, just as you'd have to do with par2.

It's a space / time tradeoff. Using par2 would result in a 45% space savings over redundant backup, but md5 is much faster than par2 on a single album, to say nothing of big chunks of your  collection. How much slower par2 is will depend on your CPU of course, and your choice also depends on how often you'll be altering your collection with tagging or adding albums and whatnot.

Backing up audio files, using Quickpar for verification

Reply #10 –
How do you figure 45%?

Backing up audio files, using Quickpar for verification

Reply #11 –
Quote from: ALiENscApE on
How do you figure 45%?


Say your music collection is 50 GB. Two copies with checksums would be 100 GB. One copy with par2 data at -r10 would be 50+5=55 GB. Thus, using par2 would use 55% of two copies, saving you 45% of the disk space in trade off for a lot of CPU time.

Backing up audio files, using Quickpar for verification

Reply #12 –
Well I basically want to have another copy on another physical hard drive anyway, so I should be ok with just md5 checksums, since I will have an entire other copy to restore from if there is ever corruption?

Backing up audio files, using Quickpar for verification

Reply #13 –
So, what program can I create md5.s with?