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Topic: Flac with QuickPar (Read 8562 times) previous topic - next topic
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Flac with QuickPar

Hello,

It's my understanding that cdr's can get messed up and have data corruption.  I saw this QuickPar program and saw what it can do.

Is putting Flac's on a CD'r by album then using the rest of the space for Par files a good idea?  Ex.  Beatles, One takes up 350Mb, and the rest of the space is Par files at about 350Mbs as well. (this is an example, i don't know how much space beatles, one takes ups...)  That's what i would do.
Also, for my other audio forms of databack up that are on my hard drive, what is a good setting for QuickPar?  I'm a bit confused about all the settings and whatnot.
Anyone have any website's or comments that could enlighten me?

Thanks

Flac with QuickPar

Reply #1 –
Yes, it is a smart approach. As long as the cd is readable at all. If the TOC gets damaged, parity is little help. However, if you can distribute your data over several CDs such that you can tolerate the loss of any one, (sounds like CD-RAID - or RACD to be exact), that's much safer.

I don't know whether QuickPar can do multiple volumes like that. I guess it can.

The general attitude nowadays is to use big slow hard drives as backup.

Flac with QuickPar

Reply #2 –
Actually it shouldn't matter if the TOC of the CDR is damaged as long as you can RIP the entire CDR using something like ISOBuster.

QuickPar will happily scan the entire ISO image for PAR2 data and undamaged blocks of file data. In order to get this form of recovery to work you need to make make a second copy of the ISO image file and rename it with the .PAR2 file extension. You then open that copy with QuickPar, and after all of the recovery data has been found, you use the Add button to have QuickPar scan the other copy of the ISO file for the file data.

It is recommended that you make the PAR2 block size an exact multiple of the CDR sector size (which is normally 2048 bytes). This will ensure that block boundaries line up with sector boundaries (and will reduce the amount of recovery data needed for a repair).

Flac with QuickPar

Reply #3 –
I've been using FLAC+QuickPar for all my audio backups.  I find that a block size of 32768 works best on my system (anything less and it takes WAY too long to run...) and I've been using 5% redundancy backing up to an external hard drive.  I figure if I start seeing bad sectors the 5% should give me enough recovery as long as I quickly move the data to another hard drive before it gets bad.

Flac with QuickPar

Reply #4 –
Quote
I've been using FLAC+QuickPar for all my audio backups.  I find that a block size of 32768 works best on my system (anything less and it takes WAY too long to run...) and I've been using 5% redundancy backing up to an external hard drive.  I figure if I start seeing bad sectors the 5% should give me enough recovery as long as I quickly move the data to another hard drive before it gets bad.

Just for clarafication: note that the 5% redundancy means that 5% of the data & parity blocks can go bad, NOT 5% of the bits in the data & parity.  For example, suppose you have 100 data & parity blocks sized 32768 bytes each, with 5% redundancy.  Now, if I flip 6 bits from 6 different blocks--that's less than 0.00003% error--you're data's toast.

The safest bet would be to set the block size to 2048 bytes, the sector size of CD.  Unfortunately, PAR2 can only have at most 32767 blocks of data & parity, so that'll give you only about 60 MB...
When a man sits with a pretty girl for an hour, it seems like a minute. But let him sit on a hot stove for a minute--and it’s longer than any hour.  That’s relativity.
-- Albert Einstein

Flac with QuickPar

Reply #5 –
Well, if I have 10,000 32,768-byte data blocks (typical for a collection of FLAC files from 1 CD), and 5% redundancy, that gives me 500 error correction blocks...quite a bit more than the 5 in your example.    So to lose my data I'd have to lose more than 500 sectors just in a single directory on my hard drive.

Flac with QuickPar

Reply #6 –
My point is, if the entire disc fails, which is possible with any media, parity is useless. If you spread data and parity on several disjoint pieces of media such that you can tolerate the loss of any one, you are much safer.

I had entire drives die because of a problem with track 0. Or, it can be the heads or the motor.

Flac with QuickPar

Reply #7 –
Quote
My point is, if the entire disc fails, which is possible with any media, parity is useless. If you spread data and parity on several disjoint pieces of media such that you can tolerate the loss of any one, you are much safer.

I had entire drives die because of a problem with track 0. Or, it can be the heads or the motor.


This is very true.  I plan on getting a 2nd hard drive to mirror the contents of my existing one as soon as I have the extra cash to pick one up.  Then, the only way I'd lose my data is in the event of both drives going into total failure at the same time, or a  natural disaster destroying my home.

Flac with QuickPar

Reply #8 –
NB Even if track 0 of a hard disk is bad (and hence the partition table is lost), it may still be possible to generate an image of the entire disk (with unreadable portions replaced with nulls in the image file). This is exactly the same procedure as programs like IsoBuster do when ripping an entire CD to an ISO file if the CD is faulty.

Once you have an image file containing everything readable from the bad hard disk, you can have QuickPar scan it for useable par2 packets, and then scan for data.

Flac with QuickPar

Reply #9 –
How exactly would that be done with a hard disk?  Is there software out there similar to isobuster, only for hard disks?

Flac with QuickPar

Reply #10 –
Quote
How exactly would that be done with a hard disk?  Is there software out there similar to isobuster, only for hard disks?

This is something I have never needed to find out, so I don't know if there is software out there that can do it or not, but I don't believe there are any technical reasons why it should not be possible.

At the end of the data, the contents of a hard disk is just a continuous stream of sectors which have be individually read. The first sector of track 0 is used for the partition table (which lets an OS know which portions of the rest of the disk have been allocated to a specific drive letter).

If the partition table is unreadable but the rest of the disk is readable, then it should be possible for appropriate software to create an image. I'm pretty sure you can do this using the Linux OS with the "dd" command.

There are of course specialist recovery companies available that can do this sort of thing for you. It is just a question of how much you are willing to pay to recover the data from the disk.

Flac with QuickPar

Reply #11 –
Maybe you are right, but I'm under the impression that hard drives are more complex beasts that use the storage for internal operations, and if that storage is damaged, they may go nuts.

My experience was that the faulty drive could not even talk to BIOS, and I don't mean bootstrap. And data recovery costs $$$, or maybe even $$$$.