Why can't I use the full disk capacity for my storage pool or volume?
Last modified date:
2026-08-27
Applicable Products
- QTS
- QuTS hero
- Storage Manager
Root Cause
QTS and QuTS hero automatically reserve part of your disk space as System Reserved space, used to store configuration information and metadata for your storage pools and volumes. This space is required for the NAS to operate correctly and cannot be freed up for regular data storage.
System Reserved space generally consists of three categories:
| Category | Purpose | Typical size |
|---|---|---|
| QNAP storage reserved space | Storage configuration data and space required for NAS functionality | About 70 GB per storage pool, 20 GB per static volume |
| QNAP RAID reserved space | RAID metadata | About 1% of each RAID group's capacity (up to 150 GB per group) |
| EXT4 file system metadata | Metadata for the EXT4 file system | Roughly 0.8%–1.8% of volumes over 100 GB |
Note
If your NAS uses Snapshot Replica, System Reserved space on the destination NAS may also include space secured for incoming backup data. This is expected and is released if you remove the associated Snapshot Vault.
Further Reading
For further assistance, ask other users and QNAP experts in the community. Go to QNAP Community
