A computer-implemented method, according to one approach, is for converting an existing storage pool into an intended storage pool in place. The computer-implemented method includes: reordering volume extents in the existing storage pool such that physical rank extents of the volumes align with boundaries between rank extents of the intended storage pool. The ranks in the existing storage pool are also converted from first rank extent sizes to second rank extent sizes. Moreover, in response to converting the ranks in the existing storage pool, for each of the volumes: a temporary pause/lock is performed on a volume segment table (VST) entry which corresponds to the given volume, and the VST entry is populated with a new structure which corresponds to the respective second rank extent size.