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Recoverable File Archiving with Free Software?

Posted by Cliff on from the redundancy-for-your-files dept.

Viqsi asks: "Back in my Win32 days, I was a very frequent user of RAR archives. I've had them get hit by partial hardware failures and still be recoverable, so I've always liked them, but they're completely non-Free, and the mini-RMS in my brain tells me this could be a problem for long-term archival. The closest free equivalent I can find is .tar.bz2, and while bzip2 has some recovery ability, tar is (as far as I have ever been able to tell) incapable of recovering anything past the damaged point, which is unacceptable for my purposes. I've recently had to pick up a copy of RAR for Linux to dig into one of those old archives, so this question's come back up for me again, and I still haven't found anything. Does anyone know of a file archive type that can recover from this kind of damage?"

4 of 80 comments (clear)

  1. Re:where have you been? by jason.stover · · Score: 5, Informative

    Here's the parchive sourceforge site .. Links to PAR2 utils, spec, etc...

  2. Par2 works great by dozer · · Score: 5, Informative

    Store the recovery information outside the archive. Par2 works really well. You can configure how much redundancy you want (2% should be fine for occasional bit errors, 30% if you burn it to a CD that might get mangled, etc.). It's a work in progress, but it's already really useful.

  3. cpio by Kevin+Burtch · · Score: 5, Informative


    True, tar cannot handle a single error... all files past that error are lost.

    On the other hand, cpio (and clones) can handle missing/damaged data without losing the undamaged portions that follow (you only lose the archived file that contains the damage). It is the only common/free format I can think of (from the top of my head) that is capable of this.

    --
    - Preferences: Solaris 10 (servers), Ubuntu (desktops), Solaris 11 (personal servers) -
  4. Re:Are you sure tar is unacceptable? by wiswaud · · Score: 5, Informative

    if you make a big tar then bzip2-it, then store the file on a CD.
    then 2 years later you want the data back.
    there's a read-error at some point within the .tar.bz2, and it gives you some garbage data.
    bunzip2 will actually be able to recover all other 900kB chunks of the original tar file, except for this missing chunk or part of it.
    Tar will just choke at that point and you lost everything past the read error. bunzip2 was able to recover the data past the error, but tar can't use the data.
    It's quite frustrating.