tape compression

[C M Reinehr]

On Friday 29 February 2008 09:57, Lonni J Friedman wrote:
> On Fri, Feb 29, 2008 at 7:10 AM, C M Reinehr <cmr at amsent.com> wrote:
> > On Friday 29 February 2008 06:41, vu pham wrote:
> >  > C M Reinehr wrote:
> >  > [...]
> >  >
> >  > >> Do I have to run any extra command to force the tape drive to use
> >  > >> compression mode ? I already tried "mt -f /dev/st0 compression 1"
> >  > >> but it does not help.
> >  > >
> >  > > What Bill says is very true, but here are some utilities that can be
> >  > > very helpful in figuring out what's going on. The tapeinfo command
> >  > > which comes in the mtx package can tell you explicitly if your
> >  > > hardware data compression is turned on or off. Check out, also, the
> >  > > scsitape command from the same package. Finally, there is the
> >  > > sg3_utils package which contains a number of useful SCSI utilities.
> >  > >
> >  > > Here's what the output of the tapeinfo command looks like on my
> >  > > system with a Tandberg LTO2 tapedrive:
> >  >
> >  > [...]
> >  >
> >  > > By the way, the command that I use to turn compression on & off is:
> >  > > mt -f /dev/nst0 defcompression 1
> >  > >
> >  > > Another thing is that with some tape drives (or so I've read) is
> >  > > that the compression & defcompression commands do not work. You have
> >  > > to set the density code.
> >  >
> >  > CM, thanks for your advice.
> >  > I just installed the package mtx, but it complains that there is no sg
> >  > devices on my server. This server is a RH9. Can I make it see the tape
> >  > drive as sg device ?
> >  >
> >  > Thanks,
> >  >
> >  > Vu
> >
> >  I'm not familiar with RH9 (I switched to Debian some years ago). The
> > /dev/sg* entries are created automagically for me by udev now. But, I
> > would imagine, if RH9 doesn't use udev, that it simply is a matter of
> > using /dev/MAKEDEV to create them.
>
> Sure, but creating them won't do any good if the kernel isn't going to
> use them.  You can create a /dev/fubar but its not going to fix
> anything.

Lonnie,

That is true, and, you will note that I confessed to not being familiar with 
RH9. That being said, my experience (admittedly much less than yours) is that 
SG device support is a standard feature of the Linux kernel. If it is not 
then he quickly & easily will find out and then either have to recompile or 
upgrade his kernel.

In the mean time, I've noticed that in this thread and others you are quick to 
criticize while offering no constructive information or support. If you know 
a solution to Vu's dilemma please share it with us. If not, I don't see that 
your criticism serves any useful purpose.

Cheers!

cmr
-- 
Debian 'Etch' - Registered Linux User #241964
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