A system includes determination of a plurality of meta-copysets of a plurality of storage devices, each of the meta-copysets including a first number of storage devices, determination of a first copyset of a second number of storage devices from a first one of the meta-copysets, where the second number is less than the first number, storage of first data in a fault-tolerant format using the first copyset, determination to migrate the first data from a first storage device of the first copyset, and, in response to the determination to migrate the first data, determine a second copyset of the second number of storage devices including a storage device from the first meta-copyset which is not in the first copyset, and the storage devices of the first copyset except for the first storage device of the first copyset and storage of the first data in a fault-tolerant format using the second copyset.