# ClusterLabs/pacemaker

Merge pull request #267 from davidvossel/require-all-docs

`Low: doc: Documention of 'require-all' option for "OR" logic in ordered sets`
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beekhof committed Mar 21, 2013
2 parents 406e1b6 + d65dde0 commit cb7b3f48dea9eb1b6825242da2ef507887b409cc
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1. +43 −0 doc/Pacemaker_Explained/en-US/Ch-Constraints.txt
 @@ -484,6 +484,49 @@ limit to the number of sets that can be specified. .Visual representation of the start order for the three sets defined above image::images/three-sets.png["Three ordered sets",width="16cm",height="7.5cm",align="center"] + +== Resource Set OR Logic == + +The unordered set logic discussed so far has all been "AND" logic. +To illustrate this take the 3 resource set figure in the previous section. +Those sets can be expressed, +(A and B) then (C) then (D) then (E and F)+ + +Say for example we want change the first set, (A and B), to use "OR" logic +so the sets look like this, +(A or B) then (C) then (D) then (E and F)+. +This functionality can be achieved through the use of the +require-all+ +option. By default this option is 'require-all=true' which is why the +"AND" logic is used by default. Changing +require-all=false+ means only one +resource in the set needs to be started before continuing on to the next set. + +Note that the 'require-all=false' option only makes sense to use in conjunction +with unordered sets, 'sequential=false'. Think of it like this, 'sequential=false' +modifies the set to be an unordered set that uses "AND" logic by default, by adding +'require-all=false' the unordered set's "AND" logic is flipped to "OR" logic. + +.Resource Set "OR" logic. Three ordered sets, where the first set is internally unordered with "OR" logic. +====== +[source,XML] +------- + + + + + + + + + + + + + + + + +------- +====== + + [[s-resource-sets-collocation]] == Collocating Sets of Resources ==

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