Re: [Xen-users] CoW works on Windows guest?

[Dan Smith <danms@xxxxxxxxxx>]

OS> Why is the .dscow file the same size as the .img file when
OS> originally created?

It is a sparse file.  It looks like it's the same size as the .img,
but it actually takes up only the amount of space it needs to store
the data you've written to it.

It is not an ideal format for file-based images, but it does work.  It
was mostly created as a simple format to use while developing the rest
of the system.

OS> create->modify->is there a way to delete the changes in the .dscow
OS> create->modify->file without openning up the domain?

You can just delete the dscow and recreate it to abandon the changes.

OS> We use /dev/mapper to map any further modifications onto the
OS> .dscow file, right? And /dev/mapper/ would be changed every time
OS> we modify on the .dscow file, right?

I'm not sure what you mean.  The /dev/mapper/foo device is a pseudo
device that redirects writes to the dscow file.  Subsequent reads to
/dev/mapper/foo show the changed version (reading the changes from the
dscow file).

-- 
Dan Smith
IBM Linux Technology Center
Open Hypervisor Team
email: danms@xxxxxxxxxx

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