How are these servers linked?

[myplanet]

Hello,

I'm perplexed by the following problem:

I have two servers in two different data centres owned by two separate hosting companies. One is running Plesk 8 and one is running Plesk 7. They were provisioned about a year apart.

... except anytime one server is rebooted or goes down... the other server does the same...

I cannot recall setting anything up that would cause this. But I definitely want to troubleshoot this issue.

Any suggestions on where to start looking?

Cheers, Jason