Hi,
20.11.2008 02:50, Evaldo Gardenali wrote:
> Hi
>
> I am trying to make Bacula work with my DVD+RW and DVD-RAM media, as raw
> devices (similar to tape, but with random r/w support,
Great idea. I'd like to see that as it would eliminate the need for
volume part files and dvd-handler and growisofs. That part of Bacula
is comparatively unstable, in my opinion. (And I wrote part of the
code and helped design the concept...)
...
...
> The following scenarios list my test experiences with Bacula 2.2.4 on
> NetBSD (I can, again, provide results with a more recent build if necessary)
...
> For the following tests, the disk was forced to SPIN DOWN before the
> beginning of each run and block sizes were chosen at random, so
> real-world speeds should be way greater.
>
> Small test to demonstrate the RW nature of the device, and the ability
> to work with offsets (expected from DVD+RW and DVD-RAM media, unexpected
> otherwise)
>
> goldstein# dd if=/dev/urandom of=1mfile bs=2k count=512
> 512+0 records in
> 512+0 records out
> goldstein# dd if=./1mfile of=/dev/cd0d bs=2k seek=2
> 512+0 records in
> 512+0 records out
> 1048576 bytes transferred in 0.774 secs (1354749 bytes/sec)
> goldstein# dd of=./1mfile2 if=/dev/cd0d bs=2k skip=2 count=512
> 512+0 records in
> 512+0 records out
> 1048576 bytes transferred in 0.919 secs (1140996 bytes/sec)
> goldstein# cmp ./1mfile ./1mfile2 || echo differ
> goldstein#
Ok.
> Test to demonstrate the random access of the device, as expected from
> DVD media.
>
> goldstein# dd if=/dev/cd0d bs=1m seek=500 count=1 of=/dev/null
> 1+0 records in
> 1+0 records out
> 1048576 bytes transferred in 1.247 secs (840878 bytes/sec)
> goldstein# dd if=/dev/cd0d bs=1m seek=700 count=1 of=/dev/null
> 1+0 records in
> 1+0 records out
> 1048576 bytes transferred in 1.518 secs (690761 bytes/sec)
What do you get when reading part of a disk that was never written to?
And how will you determine EOF and EOM conditions?
> Test to demonstrate the random WRITE access of the media (expected on
> DVD+RW and DVD-RAM, unexpected otherwise)
> goldstein# dd if=/dev/urandom bs=1k count=1 of=/dev/cd0d seek=100000
> 1+0 records in
> 1+0 records out
> 1024 bytes transferred in 3.046 secs (336 bytes/sec)
> goldstein# dd if=/dev/cd0d bs=1k skip=100000 count=1 | hexdump -C
> 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> |................|
> *
> 00000400
> 1+0 records in
> 1+0 records out
> 1024 bytes transferred in 0.001 secs (1024000 bytes/sec)
This one demonstrates that either your /dev/urandom is broken, or it's
not that simple writing raw data to and reading it from a DVD.
Arno
>
> Thanks for considering the idea
>
> Evaldo Gardenali
--
Arno Lehmann
IT-Service Lehmann
Sandstr. 6, 49080 Osnabrück
www.its-lehmann.de
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