Downtime Calculation

Downtime Calculation: Ex. A site which has only 2 hours downtime in a 30-days month will have downtime % like the following :-

D = Total downtime (in minutes)

T = Total time in the month (in minutes)

Downtime (in %) = D/T X 100

D = 2 X 60 minutes = 120 minutes

T = 30 days X 24 hours X 60 minutes = 43200 minutes

Downtime (in %)

= [120/43200] X 100

= 0.2777 %

Uptime (in %)

= 100 - 0.2777

= 99.7222 %

In other words, you have 99.722% of uptime throughout the month.

SLA % - usually calculated at 99.90% 

Outage SLA (mins.) - 167 mins. in a year

Calculation Ex: 

From 01-01-2012 to 31-12-2012 Holidays:8holidays+Fri+Sat off days adds upto 112 days holidays. So difference from day 1 of year until last day of year minus holidays = say 112 days

So total working days = 365 - 112 days = 253 working days. You may also calculate with excel formula; NETWORKDAYS.

So, Total number of minutes in working days = 253x11*60=166980

where 11 is the total business hours (may vary from organisation to org'n) in a day and 60 is for 1 hr.

So, 166980-(166980x99.90%) = 166.98 mins. Outage SLA in mins in a year for an org'n. should be around 167mins. Any downtime exceeding beyond 167 mins violates the SLA.