cli guru needed

[Les]

On Sun, 2009-08-02 at 14:38 -0400, Robert P. J. Day wrote:
> On Sun, 2 Aug 2009, Patrick O'Callaghan wrote:
> 
> > On Sun, 2009-08-02 at 12:54 -0500, Mikkel L. Ellertson wrote:
> > > Bazooka Joe wrote:
> > > > Is there a way to combine these 2 commands to cut my time in half?
> > > >
> > > > VBoxManage internalcommands  converttoraw file.vdi file.raw
> > > > then I have to run
> > > > dd if=file.raw of=/dev/sdb
> > > >
> > > > -thx
> > > >
> > > You can can command on the same command in several ways. It depends
> > > on what you put between the command.
> > >
> > > ; - always run the next command.
> > > && - run the second command only if the first command is successful.
> > > || - run the second command if the first one fails.
> >
> > How is this going to reduce his total time? The commands are still
> > running sequentially.
> 
>   i'd bump up the blocksize of that dd command.  IIRC, the default
> blocksize for dd is 512 bytes -- painfully small and resulting in lots
> and lots of little writes.  crank up the blocksize significantly and
> that second command should speed up noticeably.
> 
> rday
if the vbox command can follow fully qualified paths, you should be able
to simply say converttoraw file.vdi /pathtosda/file.raw

However, going between disks may be faster or slower, depending on the
way the command buffers the data, and/or handles disk I/O.  Personally I
think some fundamental experimentation is in order.  There is a final
issue in that some video files are protected in such a way that copying
them is prohibited.  I don't know or care about the details as I never
do anything with video.  However be aware that some driver software
includes checks for pirating video and audio.  If your driver is setup
to prohibit copying according to the DMCA, it will not work as expected.

dd may manage to copy the raw data, but again there may be information
encoded that will prevent the copy from playing.

Regards,
Les H