Can anyone point me to a cloud hosting provider who will really commit to 99.999% availability? From what I’ve seen some offer this but only back it up with meaningless compensation if they fail such as refunding a months hosting fees which for any business which really needs 99.999% availability will be out of proportion with the damage unscheduled downtime brings. The other catch that you often see is 99.999% planned availability which means that they can schedule as much downtime as they like as long as the plan it and let you know in advance.

I ask this question because although I’m very much in favour of cloud hosting I increasingly feel that where clients really need 99.999% availability they need to look at a hybrid solution which either combines your own hosting scaling out to the cloud which has been done successfully, hosting in multiple availability zones with your chosen cloud platform or maybe ultimately a multi-cloud solution spreading the hosting over two or more cloud providers, this is the only solution if you really want to engineer out single points of failure.

So while contracts often call for five nines can the client afford that extra nine, are they prepared for the complications it brings and even if they are is it more of a target than something anyone will actually commit to in application hosting today?

Any application with 99.999% availability will need to have been designed from the ground up with that availability level in mind. You can’t take an existing application and easily retrofit this level of high or rather continuous availability. In reality, if you want to upgrade an existing application from 99.99% availability to 99.999% you are going to have to engage in a serious refactoring project.