{(Subscript[𝒟, x]),(Subscript[𝒟, y]),(Subscript[𝒟, orig]),(Subscript[𝒟, repl])}={ExponentialDistribution[(1/3)],ExponentialDistribution[(1/4)],ExponentialDistribution[(1/6)],ExponentialDistribution[(1/2)]};

(Subscript[𝒟, r])=ReliabilityDistribution[x∨y,{{x,(Subscript[𝒟, x])},{y,(Subscript[𝒟, y])}}];
(Subscript[𝒟, s])=StandbyDistribution[(Subscript[𝒟, orig]),{(Subscript[𝒟, repl])}];
(Subscript[𝒟, sys])=ReliabilityDistribution[r∧s,{{r,(Subscript[𝒟, r])},{s,(Subscript[𝒟, s])}}];

tmax=15;
vfuncpar[{x_,y_},start|end|start2|end2,{w_,h_}]:={GrayLevel[0.95],Rectangle[{x-w/2,y-h/2},{x+w/2,y+h/2}]};
vfuncpar[{x_,y_},v_,{w_,h_}]:=Inset[Plot[SurvivalFunction[(Subscript[𝒟, v]),t],{t,0,tmax},Filling->Axis,Axes->None,Frame->True,FrameTicks->None,FillingStyle->Extract[Reverse@ColorData[45,"ColorList"],Position[vl,v]],Background->White,PlotRange->{0,1}],{x,y},{tmax/2,0.5},{1.5w,1.5h}];
edgefunc[points_,orig\[UndirectedEdge]repl]:={Dashed,Black,Arrowheads[Medium],Arrow[{{8.5,1},{10.5,1},{10.5,-0.2}}]};
vl={start,end,x,y,orig,repl,start2,end2,r,s,sys};
vlabels=Thread[{start,end,x,y,orig,repl,start2,end2,r,s,sys}->Map[Placed[#,Center]&,{"Start","End","(Subscript[𝒟, x])","(Subscript[𝒟, y])","(Subscript[𝒟, orig])","(Subscript[𝒟, repl])","Start","End","(Subscript[𝒟, r])","(Subscript[𝒟, s])","(Subscript[𝒟, sys])"}]];
Graph[vl,{start\[UndirectedEdge]x,start\[UndirectedEdge]y,x\[UndirectedEdge]end,y\[UndirectedEdge]end,Property[orig\[UndirectedEdge]repl,EdgeShapeFunction->edgefunc],start2\[UndirectedEdge]r,r\[UndirectedEdge]s,s\[UndirectedEdge]end2},VertexCoordinates->{{0.5,0},{5.5,0},{3,1},{3,-1},{8.5,1},{10.5,-1},{1,5},{10.5,5},{4,5},{7.5,5},{5.75,9.5}},VertexSize->{sys->{"Scaled",0.5},{"Scaled",0.25}},VertexShapeFunction->vfuncpar,VertexLabelStyle->20,VertexLabels->vlabels,Prolog->{EdgeForm[Thin],FaceForm[Lighter@LightBlue],Rectangle[{-0.6,-2},{6.6,2}],Rectangle[{7,-2},{12,2}],Rectangle[{-0.3,3.7},{11.8,6.3}],Arrow[{{3,2},{4,5}},{0,1}],Arrow[{{9.5,2},{7.5,5}},{0,1}],Arrow[{{5.75,6.3},{5.75,9.5}},{0,1.7}]},PlotRange->{{-0.6,12.1},{-2.1,11.3}},ImageSize->Medium]