An apparatus in one embodiment comprises at least one processing device comprising a processor coupled to a memory. The processing device is configured, in conjunction with an online cluster expansion process for a clustered storage system having an address space distributed across a set of storage controllers each associated with one or more storage devices, to modify the distribution of the address space across the set of storage controllers responsive to adding at least one of compute and storage capacity to the set of storage controllers of the clustered storage system. The processing device is also configured to identify a set of pending input-output requests directed to deletion of data in the clustered storage system, and to execute the set of pending input-output requests prior to relocating data in the clustered storage system based at least in part on the modified distribution of the address space.