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 12:12:02 +0000
Hi,
On 8 Dec 2007, at 10:37, Damir Dezeljin wrote:
Thanks once again,
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?
Yes, I'm aware of such a limitation and it is usually acceptable for
HSM products. If the KEXT isn't loaded, there is no data returned.
That assumes sparse file support...
You need to design your own file system that incorporates HSM as one
of its features...
I see. However, I'm concerned about Darwin updates:
- Is it possible to implement an entire file system as a KEXT in a
supported way -> so to avoid multiple KEXT releases for every Darwin
update?
Of course! Well, maybe not across major releases like Tiger to
Leopard but certainly all updates within Tiger and all updates within
Leopard can be expected to continue working as long as your kext uses
the supported KPI.
If you use internal APIs and/or unsupported APIs then things may break.
- Is it possible to implement a file system as a KEXT at all or will
I need to make the 'new file system' part of the kernel and so
recompile the entire kernel -> in such a case I can forcast kernel
installation problems or at least concern of reinstalling the kernel.
Of course it is. Many file systems are implemented as KEXTs! For
example MSDOSFS, NTFS, and UDF to name a few and they are not
recompiled each time a new kernel is released in a new update (unless
they are being updated themselves of course). If this was not the
case each software update would be huge as a lot of drivers/file
systems are KEXTs and not part of the core kernel.
Well, this wasn't a good one :) A good news would now be an Apple
commit to implement the SPARSE functionality ASAP << Am I asking too
much? :) or at least a workaround :P
You can always file a feature request bug report but given this would
require massive changes to HFS+/the kernel I doubt very much it would
be done in the Leopard time frame if at all ever... But unless you
file a feature request people will not know you want this feature so
it is definitely worth filing such a request.
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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