[Libguestfs] getting guestfs_rsync_out to work

[Richard W.M. Jones]

On Sun, Feb 08, 2015 at 12:11:37PM -0600, Jeff Brower wrote:
> With continuous loop testing, what we found is that we have to shut
> down and re-launch the image handle to see changes on the Win7 live
> guest.  Unfortunately image re-launch takes time, 3-5 sec (the image
> size is 50 GByte).  I'm assuming this is because libguestfs makes an
> internal copy of filesystem, and works from that, and doesn't
> "refresh" this internal copy until re-launching the image handle.

This isn't surprising.  Libguestfs doesn't make an internal copy of
the whole filesystem, but the libguestfs appliance will have a copy
(in its kernel memory) of any parts of the disk that rsync read.

See also:
http://libguestfs.org/guestfs.3.html#architecture

> Could we create a second partition on the guest that is much
> smaller, say 50 MByte, attach the image to that, and thus reduce the
> shutdown and re-launch time into the msec range?  Is there another
> real-time method, not using rsync?

The time to relaunch the appliance doesn't depend on the size of the
disk.

You could try hotplugging but it may not be much faster:

http://libguestfs.org/guestfs.3.html#hotplugging

I think what you really need to do is to install a backup agent in the
Windows guest and use a regular network backup.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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