On Mon, 7 May 2007, Carlos E. R. wrote:-
The Monday 2007-05-07 at 03:46 +0200, I wrote:
Yes, I saw then. I ran a few scripts that form a test suite, no errors. Now I'm preparing a dvd backup, and will add par2 files to it, too. I have to study the possible command options first.
I'm baffled...
Ok, I have a dozen of big files (roughly the same size each) in a dvd, with about 250 MB free space that I could use for par data. What options should I use to create them?
I'd use something like this: par2 c -s1024000 -c235 -l <basename.for.par2.archives> * c is to create the recovery files -s1024000 gives a recovery block size of a little under 1MB -c235 says to create 235 recovery blocks -l limits the size of the par2 recovery files to just a bit bigger than the largest file. That should create a few recovery files which, with the par2 overheads, occupy about 235MB and leave around 15MB free. Once it's finished, and if you're the sort of person that just has to be sure, you can verify the freshly created files using: par2 v <basename.for.par2.archives> And, if there's a failure after the contents has been burnt, copy the contents off the DVD using either dd or ddrescue, and then use: par2 r <basename.for.par2.archives> Now, the bad news is that for a dozen files, totalling a bit over 4GB, you may not be able to rebuild a broken file with only 235 blocks without rescuing as much data as possible from the DVD. My guess is that the files are around 350MB[0], which means you'd need at least 350-360 recovery blocks to rebuild a completely missing file. As long as only one file is broken, and you manage to recover more than a third of the data, there _should_ be enough to rebuild it. There are ways to reduce this problem, and the one I chose was to limit the size of files to 100MB[1]. That, combined with my using 535 blocks means I can have 5 completely unreadable files before I am unable to recover. And when I want to recombine the split files, I just use cat :-) [0] After rounding to the nearest MB: 4.35GB - 250MB = 4.1GB 4.1GB / 12 = 350MB [1] split -b 100M -a 3 -d <filename> <filename>. ^ That is to allow creation of names in the format filename.000, filename.001, etc. Regards, David Bolt -- Member of Team Acorn checking nodes at 50 Mnodes/s: http://www.distributed.net/ RISCOS 3.11 | SUSE 10.0 32bit | SUSE 10.1 32bit | openSUSE 10.2 32bit RISCOS 3.6 | SUSE 10.0 64bit | SUSE 10.1 64bit | openSUSE 10.2 64bit TOS 4.02 | SUSE 9.3 32bit | | openSUSE 10.3a3 32bit -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org