On Mon, Jul 18, 2011 at 2:08 PM, sirmax <sirmax@xxxxxxxxxxxxx> wrote:
> Node B with VM started:
>
> VM_IMAGE="/usr/local/virtual/img/win-xp-test-migrate.img"
> VM_NAME="win-xp-test-m"
> DEV0="kvm_m1"
>
> TMPDIR="/var/tmp/" /usr/bin/kvm \
> -hda $VM_IMAGE \
> -net nic -net tap,ifname=${DEV},script=no,downscript=no \
> -boot c \
> -vnc :15 \
> -usbdevice tablet \
> -usb \
> -snapshot \
> -monitor tcp:127.0.0.1:4415,server,nowait \
> -monitor unix:/tmp/${VM_NAME}.fifo,server,nowait \
> -incoming tcp:172.16.253.1:9999
The -snapshot command works by creating a temporary qcow2 image file
based on the disk image. In your case the effect is something like:
qemu-img create -f qcow2 -o backing_file=$VM_IMAGE /tmp/...
This temporary file is now your disk image. All write operations from
the guest will touch the temporary file and *not* the base image
($VM_IMAGE).
When you combine -snapshot with live migration QEMU creates the
temporary image before performing the block migration. Therefore the
block migration copies over all data into the temporary file (doh!).
Seems like a special case to me that would need to be carefully fixed
by performing snapshotting after block migration.
Stefan
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