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Synology software can sometimes reclaim space already occupied by your data, but it cannot create additional raw storage capacity. If you mean “expand” as in add usable capacity to a storage pool, Synology’s documented options require adding drives or replacing existing drives with larger ones, subject to the NAS model and RAID type. The free options below can help when your goal is to reduce or better manage what is already stored.
First distinguish reclaimed space from added capacity
Reclaiming space means reducing the bytes used by existing files or removing data you no longer need. Adding capacity means increasing the pool’s usable storage. Those are different outcomes: deduplication or compression may reduce occupied space for eligible data, while quotas and snapshots help manage or protect it without increasing the pool’s total capacity.
Before changing settings, identify which shared folders, applications, or data sets are consuming space. The best option depends on whether the data contains repeated blocks, compressible content, snapshots you need to retain, and whether your NAS supports the relevant feature.
Compare the software options
| Option | What it can do | Key conditions or trade-offs |
|---|---|---|
| Storage Efficiency: deduplication and compression | May reduce occupied space for eligible data. | Requires a supported Btrfs volume and compatible Synology drives; model and configuration availability, excluded data types, and performance effects apply. Savings depend on the data. |
| Snapshot and retention review | Can help you manage how much recovery history is retained; existing snapshots can constrain efficiency processing. | Snapshots may be important for recovery. Do not delete them without deciding what restore points you need. |
| Btrfs quotas | Set limits on shared-folder storage use. | Quotas allocate or constrain use; they do not increase total pool capacity. Btrfs support varies by model. |
| SSD cache | May improve performance for suitable workloads. | Requires compatible SSD hardware and does not add storage capacity; benefit is limited for large sequential workloads such as HD video streaming. |
Check whether Storage Efficiency fits your data
Synology describes Storage Efficiency as post-process deduplication and compression. Deduplication is most relevant when identical blocks recur, such as in virtual-machine images or ISO files. Compression is more promising for compressible data such as text, logs, and uncompressed databases. Neither feature guarantees a particular reduction; savings depend on the content and configuration.
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Before enabling it, verify all of the following for your exact NAS and setup:
- Your model and configuration support the feature.
- The volume uses Btrfs.
- The drives meet Synology’s compatibility requirements.
- The data types you want to process are not among the exclusions.
- The workload can tolerate the possible performance impact of processing.
Synology’s Enable Storage Efficiency documentation describes the requirements and exclusions. Feature availability depends on model and configuration, so do not assume that a setting shown for one Synology NAS will be available on another.
Plan efficiency tasks around snapshots
Snapshots can preserve versions of shared-folder data for recovery, but data referenced by snapshots cannot be processed by storage-efficiency tasks. Synology recommends running efficiency tasks before taking snapshots for the best opportunity to reduce space. Existing snapshots may limit what can be optimized.
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Use Btrfs snapshots and quotas for management, not expansion
Btrfs provides features such as snapshots and shared-folder quotas, but these serve different purposes from capacity expansion. Snapshots support recovery, while quotas let you set limits on shared-folder use. A quota can help prevent one folder from consuming more than its allowed share; it does not create additional free space in the pool.
Btrfs availability is model-specific. Consult Synology’s filesystem comparison and check your NAS model’s specifications before relying on a feature or planning a filesystem change.
Do not count SSD cache as storage
An SSD cache is a performance feature, not extra capacity for files. It can suit some random-I/O workloads, but Synology says it offers limited benefit for large sequential operations such as HD video streaming. It also requires SSD hardware, so it is not a free software-only way to expand a pool. See Synology’s SSD cache guidance and SSD cache overview.
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If eligible data cannot be reduced, you cannot safely remove or move data, and the pool has no free capacity, software alone will not expand the pool. Synology’s Knowledge Center states: “To expand a pool’s capacity, you must either add new drives to the pool or replace existing drives with ones of a larger capacity.” The supported route depends on the RAID type and NAS model; consult Synology’s pool and volume expansion instructions and verify compatibility before changing drives. The expansion article was last updated March 31, 2026.
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