My past experience with High Availabilty has been Microsoft Clustering Services. Quite often I would find links and references to HA solutions in the Unix world but never had a chance to delve deeply. Recently I came across the HA solution from IBM for their Unix Flavor – AIX. This got me hooked to it. It looks like a great solution. Google pointed me to Matilda Teams’s HACMP resources, which is nice collection of resources about HACMP. I love their FAQs section. Consider this golden nugget

Do I need a highly available cluster for my application?

The short answer is (probably): if you aren’t sure if you need HACMP then you don’t need HACMP.

The medium answer is: If you don’t know if you need a highly available cluster for your application then you almost certainly don’t (or you really don’t understand your application’s requirements in which case, you’re not ready to put your application into a highly available cluster).

The long answer (known as Jose’s Law in honour of the person who came up with it) is:

  1. Ask your manager if the application is business critical.

1a. If your manager says yes, investigate the tolerable downtime and economic loss of unavailability (you need to justify the cost of setting up an HA cluster).

1b. If the answer is no, ask his permission to investigate deeper.

  1. In either case, investigate further by first powering down the server. Wait for the calls. Say you are fixing it. Count the calls. Ask if it’s critical. Ask how critical it is.

2a. If nobody who matters complains then format the disks and install an MP3 & Quake server.

2b. If the house is on fire then go back to your manager. You need HACMP and you now have the business case to support the need.