On Thu, Oct 23, 2003 at 08:33:28AM -0700, Jason Thorpe wrote:
> 
> On Thursday, October 23, 2003, at 05:47  AM, Christian Limpach wrote:
> 
> Your examples aren't using a file system mounted on /dev/sd1a.  They're 
> using a file system mounted on /dev/mapper/vgdelight-test.  In other 

So what?  If I want snapshotting, in this scheme, I must always mount
the filesystem through the block mapper -- that does not seem at all
unreasonable to me.

Obviously, if I want to migrate an existing filesystem into the block
mapper, I can use 'dd'.  If I don't want the overhead of the mapper
itself (which, compared to all the CPU wasted by pointless calculations
in FFS, is probably pretty darned small), I can play disklabel tricks,
as Christian pointed out.

A generic block mapper seems _really_ useful.  I see no reason why it
shouldn't be in our tree, even if you believe you've got a better way
to do snapshotting in the filesystems themselves (and in the case of
at least one filesystem, I agree with you).

Christian: have you thought about how to arrange for the root FS to
be on such a device?  I assume it has an internal label of some sort
so that it carries all its metadata around with it?

Thor