Questions about dump/restore to/from DVD media

[Robert Bonomi]

> Date: Mon, 05 Nov 2012 15:42:45 +1000
> From: Da Rock <freebsd-questions at herveybayaustralia.com.au>
> Subject: Re: Questions about dump/restore to/from DVD media
>
> On 11/05/12 14:14, Polytropon wrote:
> For reference, if one did backup the whole slice/disk using dd and then 
> compressed the data, would that effectively compress all those
> 'unallocated' nodes?

NO.  The unallocated' blocks still have whatever data was in them.

*IF* you copy /dev/zero to a new file, to fill the disk, then rm
-that- file, the compression will be higher.  'How much' depends on
how empty the disk is.