NAS
NAS Still Full After Deleting Files? Check What Is Using The Space
Deleted a large folder but your NAS still reports full? Separate recycle bins, snapshots, application versions and pool allocation before removing more data or buying drives.
If your NAS is still full after deleting files, check where the space is being retained before deleting more. Shared-folder recycle bins, snapshots, application version history and background reclamation can all explain the difference. On QNAP, also distinguish free space inside a volume from unallocated space in its storage pool.
You remove an old project folder, refresh the storage screen and see almost no change. The next file copy still fails. It is tempting to delete another folder, but the first deletion may already have worked: another recovery feature can still be retaining the underlying data.
The practical aim is to find which layer owns the space, decide what must be kept and then use that layer’s supported cleanup process. The right fix may be a retention change, a completed background task or a capacity plan.
First, Check That You Are Comparing The Same Space
Keep a screenshot of the warning and the storage overview. Record the NAS model, operating-system version, affected shared folder, volume and storage pool. Note when the files were deleted and whether the system is still processing a task.
| What Looks Full? | What That Reading Can Mean | Where To Start |
|---|---|---|
| A shared folder or one user’s allocation | A folder or user quota may have been reached even if the volume has free capacity. | Check the affected account and folder limit. |
| A NAS volume | Current files, retained data, application databases and filesystem activity can consume capacity. | Review the volume’s usage breakdown and relevant applications. |
| A QNAP storage pool | Capacity can be allocated to volumes or reserved for other storage functions. | Inspect the pool, its volume types and allocation. |
| A backup destination | The backup application may retain older versions separately from the current source files. | Review that backup task’s retention and cleanup status. |
A folder-size total is not a complete account of every block used on the NAS. Avoid comparing a laptop’s visible project folders with the entire volume and assuming the difference must be a fault.
A Deleted File Can Still Be In A NAS Recycle Bin
A NAS recycle bin is separate from the bin on your computer. With a supported network recycle-bin feature enabled, deleting a file can move it into a recovery area on the NAS. The file disappears from its original folder while continuing to occupy storage.
On Synology, inspect the recycle bins of the relevant shared folders, including user home folders where applicable. On QNAP, inspect the Network Recycle Bin and its retention policy. Check the actual configuration: not every deletion route, application or shared folder necessarily uses the same bin.
Review the contents with the data owner before emptying anything. Emptying a bin permanently removes that recovery copy. When the contents are approved for removal, use the NAS interface or its supported cleanup policy and record the result.
If the bin becomes large again soon afterwards, investigate the cause. Repeated bulk imports, temporary exports or an unsuitable retention period can keep recreating the same capacity problem.
Why Snapshots Can Keep Deleted Data On Disk
A snapshot preserves a view of data at an earlier point in time. Blocks needed by a retained snapshot must remain available even when the live folder no longer contains that file. Taking a snapshot does not immediately create a second full copy of every file, but later changes and deletions can leave older blocks in use.
The live folder points to the project’s data.
A recovery point also needs the earlier data to remain available.
The retained recovery point can still need those blocks.
Suppose an old video project is removed from the live folder, but a required recovery point still includes it. Keeping those blocks is how that recovery point remains useful. The size of the deleted folder is therefore not a promise of the space immediately recovered.
Review snapshot usage and retention through the NAS’s snapshot application. Removing one snapshot may release little if other retained snapshots or the live data still need the same blocks. On supported Synology shared folders, Snapshot Replication can estimate the space associated with a selected snapshot period.
Agree which recovery points may expire before reducing retention. Stopping future snapshots does not remove the snapshots already kept, and removing recovery history is not the same as expanding storage.
Check Version History And Application Data Too
File-sync and backup applications can keep previous versions, deleted items and their own databases. These do not always appear in the folder total you first checked. Synology Drive, for example, provides storage-usage and version-management functions in its administrative tools.
Review the application responsible for the data. Check its retained versions, recycle-bin settings, backup rotation and cleanup progress. If a recording, virtual-machine or backup service uses the same storage, include its actual allocation and retention requirement in the review.
Use the application’s supported controls. Manually deleting hidden database directories or parts of a backup repository can remove recovery information or leave the application inconsistent. Identify what the directory belongs to before attempting cleanup.
There is no universal rule that keeping ten versions means ten complete copies of every file. Filesystem features and the application’s storage method affect consumption. Measure actual usage rather than multiplying the visible folder size by a version count.
A Useful Synology Check Order
- Read Storage Manager first. Identify the affected volume and pool, current capacity and any warnings or background work.
- Review the relevant shared-folder bins. Include user home folders where they apply, and keep required recovery copies.
- Check snapshots and application retention. Review Snapshot Replication and the applications storing versions or backups.
- Check reclamation on Btrfs volumes. Allow sufficient time in the configured Space Reclamation Schedule for supported background processing.
- Compare the result with the same starting measurement. Record the volume’s free capacity and whether cleanup is still running.
Space reclamation is background work, so the display may not change immediately after an approved deletion. Do not assume the operation failed and keep removing more files. If processing appears stuck, collect the task status and logs before arranging further investigation or a maintenance restart.
The Btrfs reclamation step does not apply in the same way to every filesystem or package. Use the controls for the actual volume and software instead of copying a procedure for a different setup.
QNAP: A Full Pool And A Full Volume Are Different
In QTS, a thick volume receives capacity from its parent storage pool in advance. That capacity is allocated to the volume even while some of it remains free inside the volume. Deleting files can increase the volume’s free space without returning that allocation to the pool.
That is why a pool-allocation warning can coexist with free space in a thick volume. Check what is allocated and what is actually used before treating the warning as a request to delete more project data.
A thin volume uses a different allocation approach. Supported reclamation can return unused space to its parent pool after deletions. The available actions depend on the storage configuration and software version; they are not interchangeable with the Synology Btrfs schedule.
Start in Storage & Snapshots and review the actual pool, volume type, snapshots and reserved capacity. Resizing or converting a volume is a planned storage change, rather than a routine cleanup shortcut. QNAP notes that converting a thick volume to thin is not directly reversible to thick, so assess the requirements and recovery plan before proceeding.
If you run QuTS hero, follow its storage model and documentation. The QTS thick-volume explanation above should not be used as a step-by-step procedure for a different operating system.
Match The Fix To The Finding
| What You Find | A Suitable Next Step |
|---|---|
| Approved-for-removal files remain in recycle bins | Use the supported bin cleanup, then set retention that fits the workflow. |
| Required snapshots or versions retain the data | Keep the required recovery points and plan capacity around them. Change retention only with an agreed recovery requirement. |
| Background cleanup or reclamation is still running | Allow the supported task to complete and compare the same capacity reading afterwards. |
| The pool is allocated to a thick volume | Assess allocation separately from file usage before any volume-layout change. |
| Only one user or folder cannot accept more data | Check its quota and the exact error before changing the whole NAS. |
| Useful data and required retention keep growing | Plan more usable capacity, an archive tier or another appropriate storage location. |
Keep a record of the change and its effect. “We deleted a folder” is less useful than knowing which folder, whether its bin was cleared, which recovery points remain and what the volume reported when processing finished.
When Expanding Capacity Is The Better Answer
If the remaining files and recovery history are required, repeated deletion is not a sustainable plan. Estimate net growth after normal retention has run, then allow for operating headroom and the next planned review.
For a simple planning example, 1.2 TB of usable headroom divided by 0.3 TB of net growth each month gives about four months before that headroom is consumed. This is a forecast from assumed inputs, not a measured NAS result, and it is not a target to run the system completely full.
For a DSM-based installation, review the Synology DS925+ against the workload and compatible drives. For a QTS-based installation, the QNAP TS-464 offers another four-bay platform to assess. A healthy existing NAS may only need a properly planned drive upgrade; a new enclosure is not the automatic answer.
Use the RAID calculator to compare layout and usable-capacity scenarios, then check the exact model’s drive support and expansion procedure. The NAS drive reuse and migration checklist covers the checks needed before reusing or moving existing drives. RAID fault tolerance is not a separate backup.
Frequently Asked Questions
Why Is My NAS Still Full After I Delete Files?
Deleted data may remain in a NAS recycle bin, retained snapshot or application version history. Background reclamation can also take time. On QNAP, check whether the warning concerns the volume’s actual usage or capacity allocated in the storage pool before deleting more files.
Will Emptying The Recycle Bin Always Free The Whole Folder Size?
No. A retained snapshot or another storage reference may still need some of the same data blocks. Review the approved bin contents, snapshot history and application data, then allow supported reclamation to finish.
Does Turning Off Snapshots Delete Existing Snapshots?
Stopping a snapshot schedule prevents future scheduled snapshots; it does not automatically remove recovery points already retained. Review the existing snapshots and retention policy separately, with the data owner’s recovery requirements in mind.
Why Is My QNAP Pool Full While The Volume Has Free Space?
A QTS thick volume is allocated capacity from its parent pool in advance. Free capacity inside that volume is still allocated to it. Review allocation, volume type and snapshots before deciding whether a planned layout change is appropriate.
Should I Delete Hidden NAS System Folders To Recover Space?
Use the responsible application’s supported cleanup and retention controls. Hidden folders can hold databases, versions or backup information. Removing them manually can damage the application or recovery history.
Should I Buy Bigger Drives If Cleanup Does Not Help?
Expand when required data and retention genuinely exceed the available usable capacity. First check the NAS’s supported drives, RAID layout, expansion method, backup and growth rate. Replacing drives without that plan can create unnecessary risk or expense.
Find The Retained Data Before Deleting More
Start with the warning, identify the storage layer and inspect its recovery features. Clear only what is approved for removal, allow supported processing to finish and then recheck the same measurement. If required data keeps outgrowing the system, build a capacity plan around the real workload.
For a review, bring the NAS model, operating-system version, pool and volume details, usage screenshots, retention settings and recent changes. A Support Specialist can work from those facts to discuss cleanup, expansion or migration.
