And the availability calculation formula will be:
A = A1*(1-(1-(A2*A3)n)*A4
You can play with different level of redundancy "n" of the cluster here. Currently it is 2 but you could estimate it for n=3 or n=4. That approach opens possibility to quantitatively justify you architectural decisions (not just using "best practices" or "gut feelings").
If you know MTTR for each individual component (SW and HW) you could estimate the whole infrastructure availability using this approach. But how to get that individual MTTR? From vendors - good luck! Maybe from incident records? Or set up special monitoring for that (Synthetic- robotic?)
Other useful resources with formulas that relevant to this:
BOOK
One more book: Breaking the Availability Barrier
_______________
BTW This "Saga of 9's" continuous in the next posts:
LinkedIn Discussion around Trubin's Availability Formula
The Right Number of Cluster Redundancy to Achieve the Availability Goal. Trubin's Law #4!
Cluster Availability 9's Equation
One more book: Breaking the Availability Barrier
_______________
BTW This "Saga of 9's" continuous in the next posts:
LinkedIn Discussion around Trubin's Availability Formula
The Right Number of Cluster Redundancy to Achieve the Availability Goal. Trubin's Law #4!
Cluster Availability 9's Equation
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