Method and apparatus for validating and ranking of resources that may be switched between a primary system and one or more backup systems at a single site. One embodiment provides a method for ensuring accessibility of one or more disk units by a system, comprising: configuring a disk pool for the system; validating availability of the one or more disk units for the disk pool; verifying that the disk units are at the same site as the system, and selecting one or more valid disk units for the disk pool. The method may further comprise ranking of each disk unit for the disk pool and selecting one or more valid disk units for the disk pool according to ranking.