Why did my Synology storage pool grow but my volume stay the same size?

Applies to

DSM 7.x NAS storage pools and volumes. Single-volume versus multiple-volume pool behaviour and maximum volume size vary by model and creation history.

Work through these checks

1. Open Storage Manager > Storage and select the affected pool and volume separately. Record each total capacity, available pool space, file system and current status. Check whether expansion, repair or optimisation is still running.
2. If a pool is degraded, crashed or still processing, resolve that condition first with the administrator. Do not add another operation simply because the displayed volume size has not changed yet.
3. Confirm the completed pool actually has unallocated capacity. Adding a drive to a mirrored or parity-protected layout can change protection rather than add the amount of usable storage expected. Check the exact RAID type and drive sizes against Synology's expansion guide.
4. Check the maximum single-volume capacity for the NAS and the existing volume. A volume migrated from an older NAS can retain an earlier limit; the newer enclosure alone does not prove that the old volume can reach the new model's maximum.
5. When the pool and volume are healthy and the supported limit permits it, select the volume in Storage Manager > Storage, open its upper-right menu and choose Settings. Under Modify Size, review Modify allocated size (GB) or Max, then Save only the intended allocation. Check the installed DSM version's help first.

Confirm the result

Reopen Storage Manager and confirm the intended volume capacity increased, other volumes retained their allocations, and the pool and volume remain healthy. Check available space from a client after refreshing its view.

When to contact us

Contact our Support Specialist if the expansion control is missing or the limit is unclear. Supply the NAS model, prior migration history, RAID layout and pool/volume screenshots with personal names removed.