A nice writeup of a neat (if risky) upgrade.<p>> static IPs<p>FWIW, I personally love Virtual IPs (VIPs) for this (basically, an existing network interface advertises serving more than one IP, and can change that IP dynamically between servers with an arp call). The downside is that there are a lot of cloud providers who don't support externally available VIPs. They do, however, offer their own nearly-identical solution (such as Elastic IPs from Amazon).<p>The use of VIPs or similar could have potentially avoided the need for such a risky upgrade, potentially also saving millions of dollars in the process. Of course, I could simply be missing some hidden requirement from customers that they <i>couldn't</i> use VIPs but that's pretty uncommon, even in the finance industry.