I had a question this week around what the "poweron" file is and does as someone spotted it on one of their datastores. The "poweron" file is a file that is located on the designated heartbeat data stores. The file contains the set of powered on virtual machines, this allows the master to track the state of the virtual machines, may anything occur to one of your hosts. It should be noted that the master also created a "poweron" file as the state of the virtual machines it is running will also need to be tracked. Tracking virtual machine power-on state is not the only thing the “poweron” file is used for. This file is also used by the slaves to inform the master that it is isolated from the network: the top line of the file will either contain a 0 or a 1. A 0 means not-isolated and a 1 means isolated. If a host is isolated the master will then inform vCenter about the isolation of the host.
The naming scheme for this file is as follows:
host-<id>-poweron
I hope that clarifies that file on your designated heartbeat datastores!
