If you are seeing a volume used percentage that is more than the actual amount of data that is present on the volume, this could be for a number of reasons. Some of the most common possible reasons are outlined below:
- Snapshots. If you have snapshots of your shares or iSCSI LUNs, then these will take up space. Deleting snapshots can free up space. See the How do I delete snapshots on my ReadyNAS OS 6 storage system? article for instructions on how to delete snapshots.
- Unbalanced file system. Over time, the data chunks in the file system can become unbalanced. Running a balance on the data volume can help to address this. This can be done in the web interface by going to System > Settings > Volume Schedule. Add a balance action to be run on the data volume at a suitable time.
- Fragmentation. If you have bit rot protection enabled on your shares or LUNs, then the filesystem does copy-on-write. Over time, this may lead to fragmentation in the file system. In certain cases, if there is very heavy fragmentation, then this can incur up to a 15% capacity usage overhead. Running a defrag on the volume can help. Depending on your use case, it may be necessary to move the data into a new share or LUN with bit rot protection disabled.
- Recently deleted data. If you recently deleted a large amount of data, it can take a while for this capacity to be freed up. Wait some time and then refresh the web interface. Where possible, you can also try rebooting the ReadyNAS.
Last Updated:07/08/2025
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Article ID: 26048