Hi Cheers for the guidance.

Thanks


On Fri, 2005-09-09 at 09:37 -0400, Jon LaBadie wrote:
> On Fri, Sep 09, 2005 at 09:39:31AM +0100, Chuck Amadi Systems Administrator 
> wrote:
> > Hi I have managed to config the hard disk partitions in my disklist but
> > I am short of tape space to include the remainder of the hard disk
> > partitions.
> > 
> > I had initially run the following commands is it possible to get
> > compression functioning to enable to use 40GB as opposed to native 20GB.
> > 
> > * -  amtapetype -f /dev/nst0 # determine tape type takes along time
> > * -  turn off datacompression run mt command that controls magnetic tape
> > drive operation. * -  mt -f /dev/nst0 status and mt -f /dev/nst0
> > datcompression 0 Compression off.
> > 
> > As I don't want to buy bigger tapes if possible.
> 
> Your tape's capacity is 20GB!  Not 40GB, never will be, no way, no how.
> 
> But compression (hardware or software) might be able to shrink a lot of
> data down to 20GB.
> 
> The rub is that compression algorithms, whether applied by your computer
> or by the computer in your tape drive, are only effective the first time
> they are applied.  And as PB pointed out, when fed already compressed
> data, the dumb algorithm used by the tape drive is likely to expand,
> rather than shrink, the data!
> 
> An analogy, your new 250GB hard disk drive.  If you use it to store a
> bunch of zip'ed files, does it become a 500GB hard disk drive?  No,
> it is still a 250GB drive that happens to be storing compressed data.
> 
> Similarly, your 20GB tape stores 20GB of data.  Those data may be
> 20GB of plain old uncompressed information, or a lot more information
> that is compressed by your computer before taping or by the drive
> during taping -- but not both!.
> 
-- 
Unix/ Linux Systems Administrator
Chuck Amadi
The Surgical Material Testing Laboratory (SMTL), 
Princess of Wales Hospital 
Coity Road 
Bridgend, 
United Kingdom, CF31 1RQ.
Email chuck.smtl.co.uk
Tel: +44 1656 752820 
Fax: +44 1656 752830