Comment 7 for bug 1308680

I just ran into this. It took me a bit to figure out what was happening.

I did a basic devstack+Ironic install, and registered 80 VMs (pxe+ssh) with Ironic. I hit problems immediately, even before I tried to deploy. It looks like polling the status of 80 VMs is taking long enough that the heartbeat gets missed, and updated only every ~6 minutes.

It looks like the updates happen serially, not in parallel. This is checking 80 VMs; I can only imagine what would happen if you tried managing hundreds of servers and mixed in some IPMI timeouts or the like.