[lusis]

Rollbacks are a myth. You can never rollback. Always be rolling forward. Enabling a culture and environment that allows for small frequent changes solves that problem.

The way to not impact a customer is to make deploys trivial, automated and tolerant to failure because everything fails.

[MartinCron]

Always be rolling forward

I basically agree with this idea, but when I'm selling people on the idea of making deployments trivial non-events that happen in the daytime, having the notion of "if something goes wrong, you can very easily jump back" gives people a sense of security.

In practice, when things go wrong, I've found it easier to roll forward than to roll backwards.

[kstenerud]

I've done a number of rollbacks in my time (for enterprise banking systems). They work so long as you do a few dry runs first and have an audit system in place.