Recent studies indicate that almost 59 percent of Fortune 500 companies witness IT outages of 1.6 hours per week. A company with around 10,000 employees, which pays USD 56 per hour (including salary and benefits), is losing USD 46 billion per year due to unavailability of its software solutions. (http://www.evolven.com)
According to a research by Coleman Parkes, 37,160,146 person hours are lost across Europe due to IT downtime.
In the last one decade, there has been a major shift in the way business organizations work. Most companies are actively using technology at every level to become more efficient and productive and improve their profitability. Take any industry—whether healthcare, manufacturing, social networking, media, or communication—you will be amazed at the technical solutions (a combination of software/hardware) that companies within these verticals have deployed and the critical role these solutions are playing in improving their businesses.
At the same time, though these IT solutions are adding value, they are also leading to loss of business when they are not ‘available or down’. Airlines, for instance, cannot afford outages that cause their ticket booking systems to be down, even for a few hours. Retail chains like BestBuy and eBay cannot afford outages of their e-commerce websites or billing systems around Thank Giving or Christmas.
The ‘Availability’ of a system talks about how long the system will remain up and running to serve the purpose of its end users. A system which is up and accessible to end users will be considered ‘Available’. If a system is up and due to network issues not accessible to end users, it will be considered up, but not ‘Available!’
Calculating Downtime is an intuitive way of calculating Availability. The claim that an IT solution is 90 percent available in a year (24x7x365), draws a ‘wow’ reaction. What an impressive figure—just 10 percent downtime in a year! Let’s examine this data more closely. Ten percent unavailability implies that the software is down for:
- 36.5 days in a year,or
- 72 hours in a month, or
- 16.8 hours a week or
- 2.4 hours a day
Therefore, if a system is available for 90 percent it implies that the total downtime for the target system is one month in a period of 12 months.
It has become a trend to express Availability in the count of Nines (9). For example, one nine to seven 9s (90, 99, 99.90, 99.99, 99.999, 99.9999, 99.99999). The more the nines, the more reliable and available the system is. For example, if an online banking system is available for 99.999 percent of the time, then it means the system is down only for 5.26 minutes in a year!
The following table reveals interesting facts about down time. Clearly, the more nines, the more the Availability.
And how should one calculate Availability?
To measure Availability, you need to know the Mean Time Between Failures (MTBF) and Mean Time To Recover (MTTR). Once you have this information then use the following formula:
Availability = MTBF/ (MTBF+MTTR)
The above formula will show just how much your system is available to end users. In the blogs that follow, I will be writing about the factors which result in lower availability as well as how you can calculate the MTBF and MTTR.
I have tried to briefly talk about Availability and am looking forward to hearing your opinions on the issue and taking the discussion forward.