1. A protection management method for a system of nodes, wherein each node comprises a processor, and a plurality of drives, the protection management method comprising: grouping the plurality of nodes, for each of a plurality of data protection levels which define a number of nodes to store a copy of object data, into a group of one or more protection sets being associated with the respective data protection level, wherein a given node is a member of plural protection sets being associated with different data protection levels but only the member of one protection set among the one or more protection sets associated with the respective data protection level; defining, for each of a plurality of protection levels, a plurality of protection sets being associated with respective protection levels; storing copies of first object data that has a first protection level to each node in a first protection set which is associated with the first protection level based on a protection set map, and constraining distribution of the copies of the first object data to each node within the first protection set which is associated with the first protection level; and storing copies of second object data that has a second protection level to each node in a second protection set which is associated with the second protection level based on the protection set map, and constraining distribution of the copies of the second object data to each node within the second protection set which is associated with the second protection level.