ℛhdd=ReliabilityDistribution[BooleanCountingFunction[{2,3},{x,y,z}],{{x,WeibullDistribution[4,1.25 (10^6)]},{y,WeibullDistribution[4,1.25 (10^6)]},{z,WeibullDistribution[4,1.25 (10^6)]}}];

𝒟cpu=ExponentialDistribution[1/30000];
𝒟ram=WeibullDistribution[.82,2500];

ℛServer=ReliabilityDistribution[hdd∧cpu∧ram,{{hdd,ℛhdd},{cpu,𝒟cpu},{ram,𝒟ram}}];

𝒮PowerSupply=StandbyDistribution[ExponentialDistribution[1/5000],{ExponentialDistribution[1/2000]}];

𝒟Network=ParetoDistribution[1500,10];
𝒟Cooling=ExponentialDistribution[1/5000];

servervars=Table[(Subscript[s, i]),{i,20}];
serverdists=Table[{i,ℛServer},{i,servervars}];
ℛDatacenter=ReliabilityDistribution[(And@@servervars)∧power∧(net1∨net2)∧cooling,Join[serverdists,{{power,𝒮PowerSupply},{net1,𝒟Network},{net2,𝒟Network},{cooling,𝒟Cooling}}]];

mttf=NExpectation[t,t\[Distributed]ℛDatacenter];

failures=RandomVariate[ℛDatacenter,100];

Grid[{{"MTTF","SurvivalFunction","Simulation"},{mttf,Plot[Evaluate@SurvivalFunction[ℛDatacenter,t],{t,0,100},Filling->Axis,PlotRange->{0,1},Mesh->{{mttf}},MeshShading->{Automatic,ColorData["Crayola"]["Mahogany"]},MeshStyle->PointSize[Medium]],ListPlot[{failures,{{0,mttf},{100,mttf}}},Joined->{False,True},Filling->Axis,AxesOrigin->{0,0}]}},Frame->All,FrameStyle->Gray,Spacings->{2,2},Background->{None,{LightBlue}},BaseStyle->{FontFamily->"Verdana",FontSize->12}]