[libvirt-users] Custom Live Migration Query

[Aaron Clausen]

I'm using KVM, libvirt and DRBD to come up with a custom mirroring and
live migration setup.

I have two servers, each running KVM and libvirt, and both using DRBD
to mirror guests (which are stored on raw DRBD partitions). If I shut
down a guest on one, I can easily get it up and running on the other
without issue.

I have run into some file system corruption trouble if I try to do a
live migration. I have a test script just to test out the bare
functionality I'm looking for (this script would run on the second KVM
server; kvmserv02):

#!/bin/sh

if virsh -c qemu+ssh://kvmserv01/system list | grep -q " guest "; then
  echo "Saving state on remote server..."
  if ! virsh -c qemu+ssh://kvmserv01/system save guest --running
~/guest.save; then
    echo "Could not save state of guest"
    exit 1
  fi

  echo "Setting remote drbd node to secondary..."
  if ! ssh root at kvmserv01 "drbdadm secondary guest"; then
    echo "Could not change remote host to secondary for guest's DRBD partition"
    exit 1
  fi

  sleep 5

  echo "Setting local drbd node to primary..."
  if ! drbdadm primary guest; then
    echo "Could not change this host to primary for guest's DRBD partition"
    exit 1
  fi

  sleep 5

  echo "Restoring state on local server..."
  if ! virsh restore ~/guest.save --running; then
    echo "Could not restore guest state"
    exit 1
  fi

  echo "Deleting state file on local server..."
  rm -f ~/guest.save
else
  echo 'guest not running on this host'
fi
# End of script

While the state is restored and the guest comes up on the second
server, I end up with filesystem corruptions. My first test guest had
its file system pretty heavily damaged after a few moves back and
forth.

What am I missing here? Or is this just simply a really horrible way to do it?

--
Aaron Clausen
mightymartianca at gmail.com