The terms "dependability" and "reliability" are heard throughout the data center industry, and they are often used interchangeably. Dependability is defined as trustworthy and reliable, and reliability is defined as being trustworthy and consistent. The dictionary refers to dependable as a synonym of reliable and reliable as a synonym for dependable. 

Even though these terms appear to be linked; reliability is an attribute of dependability. 

Whichever term you choose may turn into a Data Center availability conversation and that will be defined as the amount of time your data center is available and can be expressed in 9's.

These are the conditions in which we need and expect our data centers to perform and also keep in mind that availability needs both dependability and reliability.

Review the table below and see where your Data Center falls in the maturity curve of dependability.

  • Inefficient design
  • Outages/Downtime
  • Infrastructure silos
  • Hot spots and High Temperatures
  • Independent power and cooling
  • No monitoring or reporting
  • Lack of lifecycle management
  • No redundancy
  • Dedicated power & cooling systems
  • Single UPS and generator
  • Cabling and pathways lacking
  • Lack of capacity planning
  • Dedicated utility power
  • UPS and Battery Backup
  • Redundant cooling systems
  • Back-up generator
  • Redundant power
  • Redundant cooling
  • Scalable/Flexible
  • Energy efficient


After reviewing the table above where are with your dependability on the maturity curve? Are you looking for five 9's of availability?  The concept of "five 9's" availability is more of a marketing figure and doesn't always stand up in practicality. While 99.999 is impressive that may still leave you with 5.3 minutes a year of downtime.

Unfortunately, even with a substantial investment in your IT hardware and software platforms it is likely not enough to maintain five 9's unless it can be matched with the facilities infrastructure that can support the same business goals. 

Below are the actual breakdowns of the availability per the Data Center tiers availability above.

Availability %

Downtime per year

Downtime per quarter

Downtime per month

Downtime per week

Downtime per day (24 hours)

90% ("one nine")

36.53 days

9.13 days

73.05 hours

16.80 hours

2.40 hours

99% ("two nines")

3.65 days

21.9 hours

7.31 hours

1.68 hours

14.40 minutes

99.9% ("three nines")

8.77 hours

2.19 hours

43.83 minutes

10.08 minutes

1.44 minutes

99.99% ("four nines")

52.60 minutes

13.15 minutes

4.38 minutes

1.01 minutes

8.64 seconds

99.999% ("five nines")

5.26 minutes

1.31 minutes

26.30 seconds

6.05 seconds

864.00 milliseconds

The goal of most data centers is sustained continuous operation of the IT equipment. Is this within your grasp? 

Let's keep some commonsense principles in mind that will help improve the dependability and reliability in your data center.

  • Simplicity is more reliable than complexity.
  • Computers are more reliable than people.
  • Equipment performance degrades over time and use.
  • Higher quality equipment has better availability and reliability than poor quality equipment.
  • The accuracy of un-calibrated sensors and transducers decreases over time.
  • Starting and stopping equipment imparts more stress than when equipment is in stable operation.

In these cases, the goal is to deliver 100 percent computer room availability. To achieve 100 percent availability, you will need dependability. 

Two leading factors that affect the dependability and reliability of a data center: physical infrastructure and operating staff.

Let us help you find the weak links in your reliability chain and bolster your critical facilities infrastructure. Schedule a workshop with our Facilities Infrastructure Team to help evaluate and roadmap your data center to dependability.

And don't forget to meet with our Data Center practice to gain the same dependability with your IT hardware and software so that in the end your data center can truly be dependable.