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A DAS enclosure can add storage beside a NAS, but it does not necessarily enlarge the NAS’s existing storage pool or volume. The outcome depends on the NAS model, enclosure, connection, drive mode, RAID layout, and software support. Track installed drive capacity, pool capacity, and volume capacity as separate numbers so you know what the NAS can actually use.
Can I add a DAS enclosure to my NAS?
Possibly. A DAS enclosure connects storage directly to a host, but that connection alone does not determine how the NAS will expose the drives. Depending on the product, they may appear as a separate pool or volume, or they may be managed through a vendor-supported expansion path.
For example, QNAP says its TR-004 can connect by USB and serve as DAS, but on a QNAP NAS it is used as an individual pool or volume that cannot be combined with the NAS’s pool. See QNAP’s TR-004 product information. By contrast, Synology describes its RX418 as a four-bay expansion unit for compatible RackStation models, with connected drives managed through DSM; that support is model-specific, not a general promise about USB enclosures. See Synology RX418.
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Will a USB enclosure increase my NAS volume?
Not automatically. A connected enclosure can provide extra storage while leaving the NAS’s existing pool and volume unchanged. QNAP’s TR-004 is a concrete example: its pool or volume remains separate from the connected NAS pool.
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- High-Speed Data Transmission: The D4-320 hard drive enclosure (a DAS, NOT a NAS) utilizes the USB 3.2 Gen2 protocol, achieving high-speed data transmission of up to 10Gbps. When equipped with four hard drives, the actual read/write speed can reach up to 1,016 MB/s (combined read/write with four SATA III HDDs of 8TB each). With just one SSD installed, the read speed effortlessly reaches 510 MB/s (SATA III 1TB SSD). The D4-320 supports a single HDD up to 30TB, with a total capacity of 120TB, and is compatible with various hard drives, including 3.5-inch SATA hard drives, 2.5-inch SATA hard drives, and 2.5-inch SATA SSDs
- Plug-and-Play Compatibility: The D4-320 USB storage supports 4 individual disks (NO RAID function), and is plug-and-play, eliminating the need for drivers. It is highly compatible with MAC, Windows, and Linux operating systems. The USB Type-C interface supports various computer interfaces, including USB 3.0, USB 3.1, USB 3.2, Thunderbolt 3, and Thunderbolt 4
- Hot Swappable Convenience: The D4-320 HDD enclosure supports hot swapping, allowing users to replace hard disks without powering off the device. This feature enhances convenience and efficiency in data transfer processes
- Tool-Free Hard Drive Management: Featuring a tool-free hard drive tray design, the D4-320 external HDD enclosure enables easy installation and removal of hard drives without requiring additional tools. Furthermore, the D4-320 incorporates TerraMaster's unique Push-lock design, automatically securing the hard drive tray upon insertion, preventing the hard drive from falling out or disconnecting
- Efficient Heat Dissipation and Quieter Operation: The D4-320 direct attached storage incorporates an intelligent temperature-controlled fan for optimal heat dissipation. Additionally, specialized sound-absorbing panels and vibration damping measures contribute to a quieter operation, with noise levels reduced by up to 50% compared to the previous generation. In standby mode, the noise level drops below 21 dB(A), creating a remarkably quiet user environment
It helps to distinguish three capacity figures:
- Installed drive capacity: the nominal capacities printed on the drives in the enclosure.
- Pool or RAID capacity: the capacity available after the enclosure or NAS applies its RAID layout and accounts for protection and system needs.
- Volume capacity and free space: the capacity allocated to a filesystem or volume, and the portion of that allocation still free for files and services.
Synology explains that volumes are allocated space from storage pools. A pool can therefore have capacity that has not yet been assigned to a volume, and a volume can grow only when its associated pool has sufficient available capacity. Read Synology’s explanation of expanding storage pools and volumes.
Why does my NAS show the enclosure, but my available capacity did not change?
Seeing the enclosure or its disks confirms only that the NAS can detect them. It does not mean the disks have joined the pool used by an existing volume, or that any extra pool space has been allocated to that volume. Check the storage manager for the enclosure’s pool or external volume, then check the existing pool and volume separately.
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- 【Reliable External Storage System for Individuals and business】The 3.5 hard drive enclosure supports 2.5/3.5 inches HDD and SSD, max capacity up to 20TB for each hard drive, it's a ideal external hard drive enclosure for personal or enterprise using.Save space on your desktop or laptop.
- 【No heat】The sata enclosure built in Aluminum-Alloy materials and 2 inch Fan.Maximize the security of your data.Fan noise is around 40-50 decibels, not recommended if you are very sensitive to noise.
- 【Up to 5Gbps】This dual bay enclosure equips with advanced chips and USB 3.0 output interface.Transfer 1G files in 3-5 seconds with USB 3.0 Ports, which is 10 times faster than USB 2.0.
- 【Hot Swappable Convenience】The HDD enclosure supports hot swapping, allowing users to replace hard drives without powering off the device. This feature enhances convenience and efficiency in data transfer processes.
- 【Tool-Free Installation】Featuring a tool-free hard drive tray design, the external hard drive enclosure enables easy installation and removal of hard drives without requiring additional tools. Plug and play! No fuss, no muss!
Record these details before and after setup:
- Current pool size, volume size, and free space.
- Drive model, nominal capacity, and bay location in the enclosure.
- The enclosure’s RAID or disk mode and resulting pool or volume capacity.
- How much pool capacity is allocated to each volume.
- Free space reported by the NAS and by any monitoring dashboards.
- Which shares, apps, backups, or media libraries use the new volume.
This inventory keeps a new, separately managed volume from being mistaken for extra free space on an existing volume.
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There is no reliable universal number from drive capacities alone. Usable capacity depends on drive sizes, RAID layout, the enclosure’s behavior, and the NAS model. Use the vendor’s RAID calculator or configuration interface for an estimate, then record the actual pool and volume figures reported after setup.
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- 【Reliable External Storage System for Individuals and Business】The 4 Bay Hard Drive Enclosure supports 2.5/3.5 inches HDD and SSD, max capacity up to 80TB( 20TB for each hard drive), it's a ideal external hard drive enclosure for personal or enterprise using.Save space on your desktop or laptop.
- 【No heat】The 4 bay hard drive reader built in Aluminum-Alloy materials and 2 inch Fan.Maximize the security of your data.NOTE：Fan noise is around 40-50 decibels, not recommended if you are very sensitive to noise.
- 【Up to 5Gbps】This 4 bay enclosure equips with advanced chip and USB 3.0 output interface, Max 5Gbps under UASP control.Transfer 1G movie in 3-5 seconds with USB 3.0 Ports, which is 10 times faster than USB 2.0.
- 【Wide Compatibility, Plug and Play】Equipped with USB A/C 3.0 Cable Cable.Compatible with Windows 7 and above, Mac 9.1 and above, Linux.Plug and play, no fuss, no muss.
- 【Stable power supply】Equipped with DC 12V power adapter to provide stability for high-speed transmission.
If you plan to add drives to an existing NAS pool instead, first verify that its RAID type and model support the operation. Synology lists supported drive-add scenarios for JBOD, RAID 5, RAID 6, RAID F1, SHR, and certain RAID 1 configurations, while noting that supported RAID types vary by model and compatible drives are recommended. See Synology’s drive-add requirements.
Can I use any USB drive enclosure with my NAS?
No. Verify compatibility for the exact NAS and enclosure before purchase. Check the supported enclosure and number of units, interface, firmware or operating-system requirements, supported drives, and whether the intended storage mode is supported. QNAP directs users to its storage expansion compatibility list to check a NAS model and applicable enclosure count.
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- Note: When using this product, please first confirm that the hard drive loaded into this product is normal, otherwise it will lead to not out of the drive, such as loading more than one hard drive, it will only show one, can not confirm which one is bad, please load a hard drive, power on, out of the drive a, confirm that it is normal, turn off, and then load the second, in the power on, out of the drive two, to confirm that it is normal, and so on, one by one to load, until you find the The problematic hard drive. For example, if there is a problem with one of the 8 hard drives, only one drive will come out.If you have any questions, please contact me promptly.
- 【Reliable External Storage System for Individuals】The 3.5 hard drive enclosure supports 2.5/3.5inches HDD and SSD , max capacity up to 160TB( 20TB for each hard driveit's a ideal external hard drive enclosure for personal or enterprise using.
- 【No heat】The 8 bay hard drive reader built in Aluminum-Alloy materials and two 2.9 inch Fans.Maximize the security of your data. NOTE：Fan noise is around 40-50 decibels, not recommended if you are very sensitive to noise.
- 【Up to 5Gbps】This 8 bay enclosure equips with advanced chips and USB 3.0 output interface, Max 5Gbps under UASP control.Transfer 1G movie in 3-5 seconds with USB 3.0 Ports, which is 10 times faster than USB 2.0.
- 【Stable power supply】Equipped with DC 12V20A power adapter to provide stability for high-speed transmission.
Also follow the enclosure’s connection instructions. For the TR-004, QNAP recommends connecting it directly to the host rather than through a USB hub or dock. Do not assume another enclosure will behave the same way.
Should I create a separate pool or expand the existing one?
Choose based on how you want to manage the data and what the NAS explicitly supports. A separate volume can suit a distinct media library, backup set, or other data class, but it has its own capacity and failure domain to monitor. It will not automatically enlarge existing volumes or the shares stored on them.
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- 【Reliable External Storage System for Individuals and business】The 3.5 hard drive enclosure supports 2.5/3.5 inches HDD and SSD, max capacity up to 20TB for each hard drive, it's a ideal external hard drive enclosure for personal or enterprise using.Save space on your desktop or laptop.
- 【No heat】The sata enclosure built in Aluminum-Alloy materials and 2.7 inch Fan.Maximize the security of your data. NOTE：Fan noise is around 40-50 decibels, not recommended if you are very sensitive to noise.
- 【Up to 5Gbps】This 3.5 hard drive enclosure equips with advanced chips and USB 3.0 output interface.Transfer 1G files in 3-5 seconds with USB 3.0 Ports, which is 10 times faster than USB 2.0.
- 【Hot Swappable Convenience】The HDD enclosure supports hot swapping, allowing users to replace hard drives without powering off the device. This feature enhances convenience and efficiency in data transfer processes.
- 【Tool-Free Installation】Featuring a tool-free hard drive tray design, the external hard drive enclosure enables easy installation and removal of hard drives without requiring additional tools. Plug and play! No fuss, no muss!
For integrated expansion, use empty NAS bays only when the model, RAID type, and drive requirements permit it, or choose an officially supported expansion unit for the exact NAS model. Follow the vendor’s instructions before changing a live pool. Synology’s pool and volume guidance covers supported expansion paths and model-specific caveats.
Avoid spanning one volume across the NAS and an expansion unit without considering the dependency and performance implications. Synology recommends keeping volumes physically within the NAS or within the expansion unit, rather than across both, for better performance; see the DX517 product information.
How do the main expansion options differ?
| Option | How capacity is exposed | Compatibility and management | Best fit |
|---|---|---|---|
| USB DAS or RAID enclosure, such as QNAP TR-004 | May appear as a separate pool or volume. The TR-004 cannot be merged into the connected QNAP NAS pool. | Check exact NAS compatibility and mode. QNAP documents USB DAS use and enclosure RAID management. | Separately managed storage when the NAS supports it and a separate volume is acceptable. |
| Manufacturer expansion unit, such as a compatible Synology RX418 or DX517 | Vendor-managed expansion behavior varies by product and NAS model. | Check the exact compatibility list; operating-system management is product-specific. | Adding bays through a documented, supported path. |
| Drives added in existing NAS bays | Can expand an existing pool only when the NAS model and pool RAID type support it; volume allocation may be a separate step. | Drive and RAID requirements apply. | Using empty bays when the current storage layout supports expansion. |
What should I check before changing disks or RAID?
There is no single safe procedure that applies to every enclosure, NAS, and RAID mode. Use the exact model’s manual and keep a separate backup before changing RAID settings, moving disks, or disconnecting an enclosure. RAID is not a backup.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchFor the QNAP TR-004 specifically, QNAP says drive migration is limited to another TR-004; files on drives moved to or from a NAS or another device will not be recognized. Its individual mode does not support hot-swap, and the product’s stated limits include no RAID migration or capacity expansion. Review the TR-004 product information and confirm compatibility before relying on it for a particular workflow.
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