CD Backup

Verifying and Repairing

It is very important to check your backups regularly. It is my intention to check my DVD discs every six months. If I soon discover that this is too large a period between checks I will check every four.

Unfortunately files do become corrupt, especially if you are using optical media like CDs or DVDs. If you check your discs regularly hopefully any serious disc deterioration will become apparent by individual files becoming corrupt, which we can repair using our PAR2 files. If you wait for years to check your discs it is possible that they will have deteriorated so far that your PC will no longer read them. In this instance I can only suggest a program like IsoBuster - and hope that you can salvage the contents.

If your verification process leads you to discover a corrupt file it is advisable to copy all files on the disc to your hard drive, repair the corrupt file(s) using your PAR2 parity files, and then burn all files to a new disc. Using this technique - frequent checks and re-burning discs with any corruption - you should be able to maintain your archive indefinately.

Verifying

Using the Command Line

Verifying Individual Files

To verify a single file use the following command line:

MAC.EXE "E:\CDBackup\CDImage.ape" -V

Alternatively, download my batch file, ape-verify.bat. Open it in Notepad (or text editor of your choice), and amend the path in the following line to point to MAC.EXE on your PC (as you did for eac-enc.bat)

SET pathToMac="C:\Program Files\Monkey's Audio\MAC.EXE"

To use, simply drag an ape file onto the batch file's icon.

Verifying Multiple Files

Download my batch file, ape-verify.bat. Open it in Notepad (or text editor of your choice), and amend the path in the following line to point to MAC.EXE on your PC (as you did for eac-enc.bat)

SET pathToMac="C:\Program Files\Monkey's Audio\MAC.EXE"

To use, simply drag a folder onto the batch file's icon.

The batch file will verify all ape files contained within the folder or its subfolders, and will report the number of files verified, and the number that failed (if any have failed you will need to review the output to discover the files that have failed. You will also need to read the Repairing section).

Using the Monkey's Audio GUI

It is very easy to use the Monkey's Audio GUI to verify one, or many, APE files.

To verify files simply drag a single file, or a folder, onto the GUI. If you drag a folder all ape files contained in the folder, or its subfolders, will be added¹.

Select "Verify" from the command button dropdown and click to begin.

¹To include subdirectories use the "Add Folder" dropdown and ensure "Add Subdirectories" is ticked.

Repairing

If you have verified your APE files, and discovered that one or more files will not verify, it is time to discover whether those PAR2 files are really worth their weight in MB.

The PAR2 data can be used to replace corrupted parts of the APE file, if the file is not too badly damaged.

NB: You will need to transfer the APE file and all PAR2 files to your PC if you are storing on optical disc, as a repair will require that the APE file be rewritten.

Using the Command Line

To repair a file use the following command line:

PAR2.EXE r "E:\CDBackup\CDImage.ape.par2" "E:\CDBackup\CDImage.ape"

Alternatively, download my batch file, ape-repair.bat. Open it in Notepad (or text editor of your choice), and amend the path in the following line to point to PAR2.EXE on your PC (as you did for eac-enc.bat)

pathToPar2="C:\DOS\PAR2.EXE"

To use, simply drag an ape file onto the batch file's icon.

Using QuickPar

QuickPar is a freeware GUI application which will allow you to perform various PAR2-related actions, including the verification and repair of files.

The QuickPar website has a tutorial on "Using PAR2 files to verify and repair data files".

What Now?

Read my accompanying guides:

• Using EAC, MAC, TAG and PAR2 To Back-Up a CD. This guide explains how to back-up your CDs using batch files to automate the process as much as possible
• Extracting the Cuesheet from the APEv2 tag. If you need to burn back to CD you will generally need an external cuesheet. This guide explains how you can retrieve the cuesheet from the compressed file's APEv2 tag.
• Restoring to CD from the cuesheet and APE file. This guide explains a few ways to restore to CD, using your compressed file and external cuesheet
• Transcoding from a compressed image file to individual track files, or another image file. Having all your CDs in compressed image format makes transcoding to other formats, e.g.: MP3, a walk in the park... if you like Foobar ;o)

The History

Thanks to Kevin Rebarchek for his questions via email, which prompted me to write this accompanying guide. It's pleasing to hear that someone has found my CD backup guide useful, and that they are actually thinking about the process as a whole. Please email me if you have found anything on this site useful.

Document Version History