Re: Error when writing DVD-RWs
From: Jacob (Jacob_at_FAKEDOMAIN.NOTHERE)
Date: 12/03/04
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Date: Fri, 03 Dec 2004 07:07:13 GMT
On Fri, 03 Dec 2004 06:08:33 GMT, a posting issued forth from Hactar...
> Part of my laptop's hard drive is XP (NTFS), and I wanted to back it up.
> The best way I knew of (OK, the _only_ way) so it could be restored under
> Linux to a bootable state to back up the entire partition (optionally
> compressing it to save space). (Yes, I'd have to recreate the boot sector,
> but that's easy enough to do.) A bit of ssh, cat, and bzip2 later, I have
> 8.1 GB of hda1.bz2 . Realizing that that would fit onto two DVDs (I have
> DVD-RWs and an NEC ND-2510A), I used dd to cut in two approximately equal
> pieces. mkisofs won't handle files >2 GB (duh; I knew that), so I used
> split to chop it into 2047 MB chunks (split won't handle 2048 MB; probably
> could have asked for 2147483647 byte chunks, but it's not worth it).
>
> mkisofs made the ISO file, and dvdrecord burned it without incident. When
> I mount the image file loopback, it looks OK and things can be read just
> fine. But, on the resulting DVD, I see
>
> total 0
> 0 ?????????????????????????????????????????????????????/
>
> What's up with that? Do I need to get a newer dvdrecord? I tried two
> different discs, same result. I tried 1 GB chunks, same result. Am I going
> about this the hard way? What about UDF; is that not too bad to deal with?
>
> Somebody on a mailing list to which I posted this problem raised a good
> point -- if I get a single error, the archive is toast, unless bzip2 can
> deal with it. Even if bzip2 recovers, the partition image is toast, unless
> XP can deal with it. Is there a compressor with error correction, or some
> easier way to go about backing up NTFS?
>
Interesting. Without knowing what distribution you're using, or what the
DVD problem is, here's a suggested, slightly more reliable method.
Install growisofs, rar and par2.
Get your hda1.bz2 file.
Make rar archives with:
rar a -v1050m hda1.rar
which make 8 files of 1050MB (ok, the 8th is a little smaller, but I
wanted to keep you with 8, increase 1050 if you get to 9 files...)
This gives you 2 sets of 4 files totaling 4200MB=4.1GB. This leaves you
about .3GB*2=14% of the total. Run:
par2 c -r14 -u hda1.part*
Burn 4 of the rar parts and 7 of the parity volumes on each DVD. Check
sizes before burning to avoid embaressment. Use growisofs, since it
takes care of mkisofs settings for you:
growisofs -Z /dev/dvd hda1.part[1-4].rar hda1.part1.vol<foo>
growisofs -Z /dev/dvd hda1.part[5-8].rar hda1.part1.vol<bar>
Now the caveats, and additional statements:
I haven't tried any of this with files of the sizes you are using. I
don't plan too. Too much work/time. I'd be disappointed if the tools
didn't work, but it's possible.
Partimage can also work. Try:
partimage -z2 -c -o -d -V1050 save /dev/hda1 hda1.img.bz2
and use parity volumes as above for error-safety. I like the first
better, since par2 and rar are both widely used standards, and since
you're backing up Windoze, you'd be able to access your backups under
it.
That's how I'd do it. Personally, I just back up my Win2k partiton to my
second hard-drive whenever I make any changes I care about (about
yearly, since I don't use windows if I can help it). That and my windows
partition is only a couple of GB.
Oh, BTW, the partimage solution does have the elegant addition of only
backing up used blocks, thereby reducing the archive size. Depending on
how full your partition is, this may result in a space-savings for you.
Likely worth looking into.
GL
-- Jacob mailto:`echo wnpbo@urvqre.ubzryvahk.arg | tr [a-z] [n-za-m]`
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