Re: Writing to DVD
>No module ide-scsi governing the writer either ?
>
>
ide-scsi is enabled for the DVD writer. I haven't yet experimented with
writing without the use of this kernel option.
>>DVD-RAM discs can have an arbitrary filesystem placed on them and be
>>mounted. eg.
>> # mke2fs /dev/cdrom
>> # mount -t ext2 /dev/cdrom /cdrom
>> # cp * /cdrom
>>
>>
>
>I tried that with Panasonic LM-AF120U3 media.
>Seems not to work reliably with ide-scsi (MD5 errors
>when verifying content of a file), is darn slow and
>larger backups clogg the i/o buffers which then
>cannot be used for hard disk i/o.
>
>Do you get better results without ide-scsi ?
>
I haven't yet tried using DVD-RAM like this without ide-scsi. However I
have just written 2.7 GB of data to a Maxell DVD-RAM using this method
with no errors, and an average transfer rate of 1.99 MB/s.
>It appears a similar method can also be used with DVD+RW discs, however
>I have also tried writing binary streams to DVD+RW discs. For example
> # umount /cdrom
> # tar -Mcvf /dev/cdrom /some/files
> I don't understand why this works, but the resultant disc appears to be
> verbatim.
>
I have double checked this, and was able to get an average transfer rate
of 3.1 MB/s with no errors.
>Now if you dump just a raw file to the media
> cat /my/fat_file >/dev/cdrom
>and compare it with the original
> diff /my/fat_file /dev/cdrom 2>&1 | less
>does it really match ? (At least up to the
>length of /my/fat_file)
>
>
This seems to work fine. I copied a 1.2 GB file to a DVD+RW using this
method, and it verified OK. This technique gave an average data transfer
rate of 3.1 MB/s.
>I am willing to bet that you cannot mount
>on Linux a DVD written with tar cf /dev/cdrom
>
>
This makes sense. It's hard to mount a non-existant file system. :)
>I am still a bit in doubt about the
>general usability of your writing method.
>My approach would be
> tar cvzf - /some/files | \
> growisofs -use-the-force-luke -Z /dev/sr0=/proc/self/fd/0
>
>(tar option -M is still a bit obscure to me after
>reading man and info tar. Is it about end-of-tape
>handling ?)
>
>
Although using growisofs in that manner is probably a more comaptible
and reliable method, the main problem is that it can not readily split
the image across multiple DVDs on-the-fly, as far as I am aware. The -M
option of tar is to allow a tar file/stream to be split across multiple
volumes. Thus when the end of a tape is reached, a new tape can be
inserted and writing can continue. The M option appears to work when
writing to DVD as well, although I haven't yet tried it with growisofs.
Thus
# tar -Mcvf /dev/cdrom /some/files
will split the tar file across multiple DVDs if necessary. It's a bit of
a hack, but it seems to work. Also I can't seem to get growisofs to
write faster than 1x. But that's another problem altogether...
Lee
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