SSAS where are olap cubes stored
Dimensions in Microsoft SQL Server Analysis Services support either ROLAP or MOLAP.

Open the dimension in BIDS 2008, select the root dimension node 



and change this in the properties window.



For fact data you open the cube and can similarly set the storage mode by selecting a measure group and altering the storage mode to one of HOLAP/ROLAP/MOLAP in its properties window.



But this only sets the default for new partitions. You still need to go onto the partitions tab of the cube designer and set any existing partitions to the desired configuration.