[hfs-user] Embedded volume..

Simon Bazley sibaz@sibaz.com
Sat, 23 Feb 2002 00:54:37 +0000


I'm exadurating when I say it will erase the disk.
The mac won't recognise the disk as formated so at best will run a disk fixer on
it, or at worst will reformat it.  I'm guessing it would ask you if its ok
before doing this.
If you put a normal one time CD in then as you say, the mac couldn't erase it
and would just complain that it can't understand it.
If you put in a CDRW then I don't know what it would do.  I expect it would ask
you if its a new CD before going ahead and erasing it.
Id be supprised if a system with no HFS+ support knew anything about CDRW's
anyway.

Using a HFS Wrapper is nice and neat and takes up all of about 4k from your
disk, without any files on it (A default mac created HFS floppy disk image has
24k of data on it, when 2 files are present).  Its very little effort on your
part to make a HFS Wrapper for your CD, and it'd keep everyone happy.  If it was
me, I'd make the wrapper, unless you need every last k of the CD.

Simon

Entwicklung wrote:

> I noticed that the technical notes also mentioned -
> 'An HFS Plus volume is not required to have an HFS wrapper. In that case,
> the volume will start at the first sector of the disk, and the volume header
> will be at sector 2. However, Apple software currently initializes all HFS
> Plus volumes with an HFS wrapper.'
>
> Mark Day wrote :
> 'Since the Mac OS ROM only knows how to boot from HFS volumes, having an
> embedded HFS Plus volume means I can boot from it directly, rather than
> having to partition my disk with an HFS boot volume and an HFS Plus
> volume for all my data.'
>
> Simon Bazley wrote:
> 'You can create a HFS+ volume without the HFSWrapper if you
> like, but old macs will just erase the disk for you if they encounter it.
> Hence
> all new Macs use HFS Wrappers.'
>
> Going by the above  statements could I conclude that if I want to create a
> non-bootable volume (a HFS/HFS+ CD-ROM to be specific) I don't need to
> consider using an embedded volume at all?
>
> I have a couple of questions to what Simon wrote - If my external HFS+
> volume happens to be on a CD-ROM which is in any case a one-time writable
> medium, how could older macs 'erase' the disk? I guess that probably happens
> to CD-RW's which can be formatted or erased..... or did you mean something
> else ?
>
> And if I do have a wrapper on a HFS+ volume and insert it into an older Mac,
> it would anyway not be readable though it doesn't get erased, right ?
>
> Regards,
> Nandini Hengen