On Dec 31, 2009, at 11:58 AM, Michael Ben-Nes wrote:
To avoid changes on the fly its possible to use snapshot.
I am wondering, what will happen if ill feed dd through gzip. Will
it compress the empty spaces ?
At that level there are NO empty spaces. Every block has something in
it. What you call empty space is just blocks that have not been
allocated to a file.
If the disk has never been used since the last full format, the blocks
contain zeros, and will compress to almost nothing. As the disk gets
used, the blocks continue to contain the same data they did when they
contained files, unless you erase files as you delete them. I know
MacOS has such an option if you empty the trash, but the base
operating system underneath (BSD) does not.
I've never heard of there being a Linux option to do so, but there
might be.
I still don't understand this fascination with DD. It produces an
image of the file system, but does anyone really want that? Unless you
are going to place it back on the same device, or an exact duplicate,
it's not very good. You can easily end up with an unreadable file
system, empty space, etc.
The only advantage I can see to doing it is that you don't have as
much overhead because you are not opening each file. A single read
error will crash the backup. Better IMHO to use tar or rsync.
Geoff.
--
geoffrey mendelson N3OWJ/4X1GM
Jerusalem Israel geoffreymendel...@gmail.com
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge
or understanding, as in he has a sub-wikipedia understanding of the
situation. i.e possessing less facts or information than can be found
in the Wikipedia.
_______________________________________________
Linux-il mailing list
Linux-il@cs.huji.ac.il
http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
