[hfs-user] Embedded volume..

Simon Bazley sibaz@sibaz.com
Fri, 22 Feb 2002 13:51:47 +0000

I'm not sure exactly what you're referring to, but heres a few pointers.

The volume is the thing that you mount on your computer which provides
files.  It represents the single mount point which appears as a disk on
your computer.
The HFS Wrapper is a HFS partition consisting of a massive consecutive
bad block file, which happens to be a HFS+ partition thats embedded in
the HFS volume.
The important difference between HFS+ and HFS is that wheras in HFS
certain files (Device Drivers, Boot System Files, Allocation Bitmap)
exist at various physical disk locations (sector 0, sector, sector 4
etc) and the MDB only gives the location to the Catalog and Extent
files.  Also there are 2 different address spaces, physical (in
sectors), and logical (in blocks, starting at 0, after the end of the
volume bitmap, at the location described in the MDB as the start of free
space).  HFS+ has very little (if any) system files at fixed locations,
and everything is referred to in the volume descriptor (replaces the
MDB), in the way the Catalog and Extent files was before.

Hope that explains everything, if not give me the names of the variable
in the HFS and HFS+ volume descriptors and I'll explain what they mean.


Entwicklung wrote:

> Hi,   what exactly does the term embedded volume mean? I've noticed
> that the HFS MDB has some fields related to this but the HFS+ volume
> header doesn't seem to. I'm not really using these fields but I'd like
> to know what they're used for in any case. So if anyone could
> enlighten me I'd appreciate it. Regards,Nandini Hengen