[Qemu-devel] Re: [PATCH] Snapshot block device support

[Fabrice Bellard]

I had plans to implement "copy on write" disk images...I find your 
approach original. My initial plan was just to add a second disk image 
for each disk containing the changes. It should be easy to do it from 
your code (for example by adding options '-hdacow file' where file is 
the snapshot file you use).

About IDE, it is working (at least with kernel 2.4.20). Someone has even 
compiled a linux kernel inside QEMU (slowdown factor of about 15), so vl 
begins to be usable for real tasks. There are still known problems if 
several processes use floating point at the same time.

Fabrice.

Rusty Russell wrote:
> Hi Fabrice,
>
>         I haven't got the IDE emulation to work for me yet (is it
> supposed to yet?), but this allows the "-snapshot" option and "C-a s"
> to commit the disks.  The blocks which change are committed to backing
> store, and a bitmap of changed blocks is kept.
>
> Diff + new test file below.
> Rusty.