Re: Sparse files on Mac
Re: Sparse files on Mac
- Subject: Re: Sparse files on Mac
- From: Anton Altaparmakov <email@hidden>
- Date: Sat, 8 Dec 2007 10:24:45 +0000
Hi,
On 8 Dec 2007, at 10:15, Damir Dezeljin wrote:
The main question is WHY are you trying to do what you are trying
to do?
I'm working on a HSM (Hierarchical Storage Management) product. The
lack of sparse file support seems a big show stopper for
implementing such an application.
I saw HFS and HFS Plus support resource forks - I'm wondering if the
mentioned functionality can be used to display a different file size
to the user than the 'real' size of the file on disk. Let suppose
the file is truncated to zero length, but I still want to show the
original size to the user. Is there any way (also not supported one)
to do this?
No you cannot do that.
You cannot put an HSM application on top of an existing file system or
at least not in a reliable way. For example what happens if people
access the underlying file system without your HSM KEXT loaded?
You need to design your own file system that incorporates HSM as one
of its features...
If you don't want to design a file system from scratch you can just
take one of the existing ones and modify it so that it supports HSM
and then copy its file system driver and modify that to support HSM.
Then your product would be the new file system driver + management
tools + a "newfs"/"mkfs" application to allow people to create such
file systems. (Don't forget to rename the file system so it does not
clash with the original one!)
But note as things stand at present Mac OS X does not allow booting
from a kext based file system so your users would not be able to have
their boot file system be your file system.
Best regards,
Anton
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer, http://www.linux-ntfs.org/
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