Like others, I have had problems making large-scale backups by dvd+rw-format �ing, mkudffs �ing, and mounting a DVD+RW -- then copying to the media.
a) When it worked, it took too long for filesystems with a lot of files (copying small sets of large files works OK, with a lot of files, performance seems to slow to a drip)
b) It didn�t always work, spuriously resulting in �media errors� about when I mounted the volumes, at times (this is with an �Optorite� DVD+RW drive)
Another options -- growisofs �Z �dvd-compat /dev/scd0 �udf /home/my/files -- is insufficient, due to the �alpha� implementation of the UDF filesystem in mkisofs (symlinks, ownership gets trashed)
Therefore, I use the following procedure (with Andy Polyakov�s patch applied) to perform backups:
a) dd if=/dev/zero of=a_temporary_file.img bs=32k count=143432
The above generates an empty image file (a_temporary_file.img) the size of a DVD+RW.
b) mkudffs �spartable=2 �media-type=cdrw a_temporary_file.img
The above then formats the image file with the UDF filesystem.
c) mount �o loop �t udf a_temporary_file.img /mnt/udf
We then mount the filesystem image onto /mnt/udf so we can copy files to it.
d) cp �rv /home/my/files /mnt/udf
This copies (recursively) the files onto our temporary image file. . .
e) umount /mnt/udf
f) growisofs �dvd-compat �Z /dev/scd0=a_temporary_file.img
. . . which we then burn onto DVD+RW in a single, speedy pass!
I find this method very useful for generating UDF DVD backups � the benefits are:
1 � It�s reasonably fast; the growisfs executes at the appropriate speed and the cp is pretty quick
2 � The DVD+RW�s can be mounted �live� with �mount �o rw,noatime /dev/scd0 /mnt/cdrom � so that as the kernel patch stabilizes, the backups can be modified at-will (I�ve tinkered with my backups just to verify that it works)
3 � Symlinks and ID�s survive the process
4 � I have a much lower failure rate with DVD+RW media using this method vs. dvd+rw-format/mkudff/mount/cp (and I have been verifying my data, of course)
Anyone have any thoughts on this method?
-Tony
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