7x24

If you've been around in IT for a while you've probably come across the term 7x24 meaning 100% system uptime.

I was once employed in London by a Investment Bank as a DBA where we were developing a mission critical global options trading system. Luckily the data volumes were small, the servers and environments stable and I'd had plenty of time to work through a reliable hot standby failover solution with an excellent UNIX Sysadm. All was good in my world.

Then during the preparations for go-live the topic of Availability arose. The Project Manager threw into the mix that we had to guarantee 7x24 availability.

My response was that we could aim for 100% uptime excluding planned outages but that we couldn't guarantee it. This resulted in a bit of table-thumping, as was quite often in IT projects in an Investment Bank.

Suffice it to say that when I explained the costs and complexities involved in guaranteeing high that availability from a solutions side and the human side it the PM became a bit more reasonable, especially when I threw in the fact that neither Scott McNealy nor Larry Ellison could guarantee 100% uptime on the configuration of Solaris and Oracle that the solution was constructed.

So the lesson is that before you start discussing High Availability the metric that needs to be understood is the actual cost, either in dollars or reputation, to your business of the mission critical app being unavailable. Until you have that there's really no point in discussing the HA requirements of the system. The funny thing is that when I was consulting I designed lots of Technical Architectures and never once could I get that fact out of the client.