tcopy

[Jeff Vian]

On Wed, 2004-09-15 at 10:32, Fritz Whittington wrote:
> On or about 2004-09-15 08:20, Will McCorkle whipped out a trusty #2 
> pencil and scribbled:
> 
> >Nope, when I run dd the drives just sit there and do not respond. I can
> >run dd and pull information from the drive and write to them, but
> >sending information from one to the other is not working.
> >
> >Thank You
> >Will McCorkle
> >Systems Administrator
> >DG Systems
> >wmccorkle at dgsystems.com
> >972-581-2119
> >
> >-----Original Message-----
> >From: fedora-list-bounces at redhat.com
> >[mailto:fedora-list-bounces at redhat.com] On Behalf Of Patrick Boutilier
> >Sent: Tuesday, September 14, 2004 3:37 PM
> >To: For users of Fedora Core releases
> >Subject: Re: tcopy
> >
> >
> >
> >Will McCorkle wrote:
> >  
> >
> >>Yes, the data is put on the tape in 18 images using tar.
> >>    
> >>
> >
> >Have you tried dd ? This command might work (substitute real /dev
> >devices).
> >
> >dd if=/dev/tape1 of=/dev/tape2
> >
> >
> >
> >unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list
> >
> >
> >  
> >
> Well, I don't suppose you have enough disk space around to read one 
> tape, write to a disk, and then read the disk with dd and write to the 
> other tape? 
> 
> Seems if you can both read and write tape, but not both at once, you 
> could do:
> dd if=/dev/tape1 of=/tmp/xxxx
> dd if=/tmp/xxxx of=/dev/tape2
> 
Be careful.  AFAIK using the dd command to copy to a tape may overwrite
the tape formatting. This will not be nice if it makes the tape
unusable.

The OP said he used tar to create the tapes.  Why not use tar to copy
tape to tape? (and avoid potential problems with formatting of the tape)

# tar -xOf /dev/tape1 | tar -cf /dev/tape2 - 

> (I'm guessing from your description above that the controller is only 
> capable of having one tape drive in use at a time.)
> 
> You should almost certainly use ibs and obs to set some large blocksizes 
> or else it will take halfway to forever to do the job.  Optimal 
> blocksize would be the blocksize that was used to write the tape, or 
> even better an integer multiple of it, if you have the ram.
> 
> If you really don't have enough disk space, you could use the seek=, 
> skip=, and count=  options to dd to copy large chunks at a time.  See 
> the man page for dd, or the info file.  "info coreutils dd"  gives some 
> helpful examples.