Comment 3 for bug 1450874

Hi Jesse. I ran the same tests in our environment:

1. Booted a cirros image, landed on compute03
2. Issued continuous ping from DHCP namespace
3. Issued a 'nova resize <instance> <flavor>'. Nova put instance into RESIZE state, new instance landed on compute04. Neutron unplugged tap from brq bridge on compute03. Tap was plugged into brq bridge on compute04.
4. Continuous ping from DHCP namespace resumed after 68 seconds. Nova state was VERIFY_RESIZE.
5. Waited 2 minutes. Issued a 'nova resize-revert <instance>'. Tap removed from brq on compute04. Tap plugged into brq on compute03. Nova put instance immediately into ACTIVE state.
6. Continuous ping from DHCP namespace resumed after 62 seconds.

Considering the time it takes to make a snapshot, copy it from one compute to the other and boot it, 60 seconds could be reasonable. Until you confirm the resize, the old instance remains on the old compute node in /var/lib/nova/instances/<instance>_resize. This is probably why it recovers quickly when you do a 'nova resize-revert'. When you issue a 'nova resize-confirm <instance>', that old data gets removed and the state goes from VERIFY_RESIZE to ACTIVE.