Is there an industry standard way of calculating downtime for a service?

[SeanO]

Hello everyone,

I’m looking to find out if there is an industry standard way of calculating downtime for a service, in an organisation. Instead of a complete loss of services, or particular capability going down such as security cameras. If we had an outage of a particular vendor for a 5 hour time frame on a working day. Impacting 200 out of 10,00 people.

How do we quantitively asses this and assign a value, are there any known formulae or standard ways of doing this? I can make one up to calculate, but, I’m looking for an industry standard one, as this is likely to be contentious.

Thanks & regards,

Sean

[dcontesti]

Here are a link that might help you:

https://www.techtarget.com/searchdisasterrecovery/tip/How-to-calculate-maximum-allowable-downtime

I believe that you are looking for maximum tolerable downtime (MTD) which is determined through a business impact analysis (BIA) and a comprehensive risk assessment. 

"MTD is the maximum amount of time a business can tolerate a system or application being unavailable. It's an operational determination that's based on the impact on business functions, and the costs and lost revenue that might occur. 

To calculate MTD, business continuity planning teams add together three metrics: Incident response time (IRT), Recovery time objective (RTO), and Operational resumption time (ORT). "

Hope this helps

d

[Steve-Wilme]

Generally it would be covered in a service schedule to a contract with a supplier.  Many suppliers will express it informally as a target service availability percentage e.g. 99.95% from which you can derive downtime per period.  So 99.95% is about 4 1/2 hours downtime per year.  There will normally be a specification of the calculation in the contract.  

Most service contract will exclude any downtime for planned maintenance from the calculation.

They may also cite an availability figure for hours of service only, when services are not 24/7.

The events force majeure clauses, if any, will also be relevant as will any service credit regimen for failure to hit the targets.

[SA3]

Does this help?

MTD (Maximum Tolerable Downtime) is the sum of RTO (Recovery Time Objective for hardware) and WRT (Work Recovery Time to fully configure the system and software).

Mean Time Between Failure (MTBF) is the average time until a component fails.

Mean Time to Repair (MTTR) is the average time it takes to repair a failed system.

For example, if MTD is 4 hours and MTTR is 3 hours.