If I understand what you're trying to do, I don't think you need to
recreate the entire stack. You should be able to subclass
IOBlockStorageDevice and give it whatever backing store you want.
I can provide you with some code that shows how to do this if you need.
-Rob
--
Rob McKeever, email@hidden
Mass Storage Group, CPU Software Engineering
Apple Computer
On Feb 21, 2008, at 5:47 AM, Valentin Slavov wrote:
Hello
I need to develop a virtual block device which will be used for
testing filesystem operations with files larger than 16TB or so.
Obviously all this space should be virtual (in a sparse image sense),
however there should be some kind of backing store to hold the
filesystem meta data. Since meta data is written at different places
in the volume (hfs+ keeps a backup at the end of the device and so on,
a backing store for certain "ranges" should be used. The backing
stores should be configurable (I was thinking of providing bsd names
and searching the I/O Kit registry for IOMedia objects, and attaching
them to my driver). Another solution would be to implement the driver
as a filter scheme but this is inflexible since backing store cannot
be configured easily.
Although the first solution seems more appropriate, I need to
implement a whole driver stack for virtual devices (like the apple
disk image drivers), but unfortunately I can't find sufficient
documentation for this task. I'd like to know if there are more
appropriate solutions and other hints that might be useful.
Thanks in advance
V.
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