[hfs-user] Embedded volume..

Entwicklung entwicklung@whengenibk.de
Fri, 22 Feb 2002 15:07:55 +0100


Oops ...sorry! the second field was meant to be drEmbedExtent... wrote that
in a hurry!

-Nandini

----- Original Message -----
From: "Entwicklung" <Entwicklung@WHengenIBK.de>
To: "Simon Bazley" <sibaz@sibaz.com>
Cc: <hfs-user@lists.mars.org>
Sent: Friday, February 22, 2002 3:05 PM
Subject: Re: [hfs-user] Embedded volume..


> Hello,
>      Thanks for replying... was hoping that someone would respond!
>
>         I was referring to the fields:
>   UInt16 drEmbedSigWord ;//embedded volume signature - formerly drVCSize
> and HFSExtentDescriptor drEmbedSigWord ;//embedded volume location and
> size - formerly drVBMCSize and drCtlCSize
>
> I think what you mentioned about Wrappers is relevant to what I wanted to
> know though I don't see the purpose of having a HFS+ partition embedded in
a
> HFS volume (?). Why would anyone want an embedded partition when all data
> could be stored in the original HFS partition? I've just set these fields
to
> 0 right now and I fail to see a situation where I (a third-party
HFS-volume
> developer) would ever need these.
>  Any tips?
>
> Regards,
> Nandini Hengen
>
> ----- Original Message -----
> From: "Simon Bazley" <sibaz@sibaz.com>
> To: "Entwicklung" <entwicklung@whengenibk.de>
> Cc: <hfs-user@lists.mars.org>
> Sent: Friday, February 22, 2002 2:51 PM
> Subject: Re: [hfs-user] Embedded volume..
>
>
> > 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.
> >
> > Simon
> >
> > 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
> >
>