Random data placement has recently emerged as an alternative to traditional data striping. From a performance perspective, it has been demonstrated to be an efficient and scalable approach for largescale storage systems. In this study we address the challenge of effectively managing the physical size of large data repositories. Specifically, we define the disk replacement problem (DRP) as the challenge of finding a sequence of disk additions and removals for a storage system while migrating the data and respecting the following constraints: (1) the data is initially balanced across the existing configuration, (2) the data must again be balanced across the new configuration, and (3) the data migration cost (either the amount of data moved or the elapsed time) must be minimized. Removing and adding disks in a large storage system may be required when devices are approaching the end of their life span (i.e., old disks are replaced with new ones) or when applications require increased sto...