Re: [cygwin] Re: Is a disk image created within dd "safe"?

[Eric Blake <eblake at redhat dot com>]

On 09/02/2015 04:23 PM, Jason Pyeron wrote:

>> There are various solutions that CAN capture an accurate 
>> point-in-time disk snapshot.  
> 
> For cygwin/Windows use the Volume Shadow Service (VSS). I have used (XP)
> cygwin dd and rsync to take (clone) images from the VSS managed drive.

What's more, if you are running your Windows machine as a virtual
machine on top of qemu/kvm, you can install qemu-guest-agent into your
Windows setup, and set things up so that when the hypervisor wants to
take a snapshot of your guest, the guest-agent can coordinate with VSS
to make the point in time correspond to completely stable I/O (all
databases flushed and so forth, so the captured disk state is stable as
if you had gracefully powered off) rather than just a random state of
unflushed I/O (the disk state is as if you have yanked the power cord,
and may have missing transactions; hope your file system had decent
journaling if you wanted it to be consistent).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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