Appending tp LTO 4 media

[bogstad-e+AXbWqSrlAAvxtiuMwx3w at public.gmane.org (Bill Bogstad)]

On Fri, Apr 2, 2010 at 1:06 PM, Stephen Goldman <sgoldman-3s7WtUTddSA at public.gmane.org> wrote:
> Good morning Blu,
>
> ? ? ? ?We purchased a HP LTO 4 to store image files for long term storage I 've ?training myself how to move the directories over .
>
>
>
> tar -czf /dev/st0 /directory copy
> tar -tvf /dev/st0 > tape.list list of the tape
>
> tar xvf /dev/st0 090203 ? ? restore a directory
>
>
> I 'm not sure how to append to the existing tape ?
>
> Do you need to move to the end of the data - <mt -f/dev/st0 eod>

I think you mean eom.  (Although it's been a while since I did
anything with tape.

>
> Then
>
> tar -czf /dev/st0 /directory copy
>
> Determine available space left on the tape

This is actually a hard thing to do with tape since all modern drives
do internal compression and there is no way to know for sure how
compressible your data stream will be.  You mention image files above
and if they are already compressed the drive compression is likely to
do you little or no good.   You either need to test things out with
representative samples of your data or assume that you will get
minimal or no compression.  (i.e. Your "800Gig" tape just became a
400Gig tape.)

Bill Bogstad