Tag Archives: high availability planning

Blue Skies & Rain, Sunshine & High Availability Platforms


We all wish for blue skies and sunshine!

When your computers are running great and the your servers are humming along fine, your work environment cam  seem like blue skies and sunshine. However, planning for the day when server or workstation hard drives fail is more important than just your average backup planning. No, we are not talking about Disaster Recovery Planning this time, or your overall Business Continuity planning, but instead, your high availability planning, or just plain High Availability (HA)

In other words, how do you make sure that your critical servers and computer workstations stay up and running when hardware fails? How do you keep those critical server applications available when a server decides to take a dive? Ordinary backup can take a long time to recover and often does not include the very latest data. In addition, backups do nothing in the immediate when you lose hardware.

The answer: High Availability Planning.

Saving for a rainy day is all well and good, but isn’t it better to build a roof with gutters? High availability platforms provide your organization with the ability to absorb the unexpected stormy days and computer hardware crashes and keep you resiliently speeding along without missing a beat.

The goal of any high availability platform, or (environment), should be a minimum of 99.999% also referred to as the “five nines” That means no more than 5.26 minutes of total platform downtime per year as show in the chart below:

Availability % Downtime per year Downtime per month* Downtime per week
90% (“one nine”) 36.5 days 72 hours 16.8 hours
95% 18.25 days 36 hours 8.4 hours
97% 10.96 days 21.6 hours 5.04 hours
98% 7.30 days 14.4 hours 3.36 hours
99% (“two nines”) 3.65 days 7.20 hours 1.68 hours
99.5% 1.83 days 3.60 hours 50.4 minutes
99.8% 17.52 hours 86.23 minutes 20.16 minutes
99.9% (“three nines”) 8.76 hours 43.8 minutes 10.1 minutes
99.95% 4.38 hours 21.56 minutes 5.04 minutes
99.99% (“four nines”) 52.56 minutes 4.32 minutes 1.01 minutes
99.999% (“five nines”) 5.26 minutes 25.9 seconds 6.05 seconds
99.9999% (“six nines”) 31.5 seconds 2.59 seconds 0.605 seconds
99.99999% (“seven nines”) 3.15 seconds 0.259 seconds 0.0605 seconds

As you might imagine 99.999% up time is a difficult target to reach, but ever more relevant in today’s “need it up and running right now” computing environment.

Wouldn’t it be nice if everything were in the “five nines” category. Think about it driving, no oil changes, no gassing up the vehicle, no red lights, not stopping for anything except perhaps a NASCAR tire change one per month. Ahhhh! That would be nice.

The truth is that most computing environments fall far short of the elusive 99.999% goal and most environment are lucky to hit a better than 97% goal overall. However, most environments don’t need to include every piece of IT technology in their High Availability (HA) solution.


For example. Do you need to include your fax machines and printers? The old computers that are not critical to the environments operations? How about laptops, or vendor equipment? Perhaps some of these items will not be counted in your (HA) plan and you can automatically exclude them and focus on the critical items.

For many organizations a typical very basic (HA) plan for their IT environment might look like this:

  • 9 out of every 10 servers included in the plan
  • 1 out of every 10 workstations included (because most employees can be moved to another workstation or a replacement is readily available)

*Network equipment sometimes has redundancy, but often times is not completely redundant and represents a Single Point of Failure in many organizations.

**Communications lines and links to the outside work are usually not redundant in most smaller environments and also represent Single Points of Failure and can represent significant downtime.

High Availability represented in the simplest way look like this:

Data : Redundant  – Servers : Redundant – Workstation Functions : Redundant

There are many ways to implement (HA) and many different platforms to choose from. However, the most important thing you can do is educate yourself and make certain that your IT firm are experts that are well trained to adequately serve your needs.