USB DAS for NAS backups: QNAP TR-004 vs TerraMaster D4-320

Your NAS needs a second copy, not necessarily a second NAS. A four-bay USB DAS gives you somewhere to put backups without another network address, operating system or set of apps to manage. Plug it into a supported host, choose the disk layout, and let your backup software do the useful part.

Choose the QNAP TR-004 for hardware RAID and QNAP’s disk-management tools. Choose the TerraMaster D4-320 for four independent disks and a 10Gbps USB connection. The big question is whether you want one enclosure-managed RAID volume or separate destinations for your backup jobs.

Specs and operating instructions from QNAP, TerraMaster and WD; verification and restore guidance from the software projects, checked October 25, 2026.

Want a smaller offline layer alongside the DAS? Our Blu-ray archive guide turns selected photos and documents into labelled discs with a checksum-and-restore workflow.

TR-004 vs D4-320: the useful differences

Enclosure and best fit	Disk modes, connection and management
QNAP TR-004: choose it when you want the box to manage a RAID group and present that storage to the host.	Four SATA bays, diskless. Individual, concatenated JBOD, RAID 0/1/5/10, plus Software Control configuration. USB 3.2 Gen 1, 5Gbps, Type-C. TR-004’s drive slots operate at SATA 3Gbps and accept backward-compatible SATA 6Gbps drives. Windows/macOS/Linux host use; External RAID Manager runs on Windows/Mac, with native management on supported QNAP NAS systems. One 120mm smart fan.
D4-320: choose it when you want your backup tools to see four separate disks, without hardware RAID in the enclosure.	Four SATA bays, diskless; four individual disks, no hardware RAID. USB 3.2 Gen 2, 10Gbps, Type-C. Accepts 3.5-inch SATA HDDs, 2.5-inch HDDs and SATA SSDs. Maker lists Windows, macOS and Linux. One temperature-controlled 120mm fan. RAID, if you choose it, comes from host software rather than a switch on this box.

The QNAP product page, desktop enclosure manual and TerraMaster specifications supply the hardware details. The USB connection is shared by the populated bays; the D4-320’s higher interface rate gives more host-link headroom, while the drives, host and backup workload determine the transfer you get.

On a NAS, choose a supported external-storage filesystem and backup application before loading the enclosure. Confirm that your intended disk mode appears as a usable backup destination. For the wider choice between a prebuilt NAS and attached storage, start with our NAS buying guide.

QNAP: hardware RAID, with a naming trap

QNAP’s Individual mode exposes each disk separately. Its JBOD mode joins disks into a single linear volume. Those are different layouts, even though people often use “JBOD” casually to mean any box full of disks.

Choose RAID 1, 5 or 10 when you want the enclosure to handle disk redundancy. QNAP’s Software Control setting lets a supported utility or QNAP host configure the enclosure; the RAID engine is still in the box. It doesn’t turn the TR-004 into a host-managed mdadm array. For a Linux host, use the rear mode switches or configure the group through a supported Windows/Mac or QNAP platform first.

Set the layout while the drives are empty. Changing RAID modes can erase the drives, and the TR-004 doesn’t offer RAID-level migration or capacity expansion. QNAP also says Individual mode does not support drive hot-swap. Use the manual’s mode-specific procedure rather than pulling a live disk because the tray has a handle.

For a NAS backup destination, keep the distinction between External Storage and QNAP’s NAS Storage expansion mode clear. The latter has additional restrictions, including no Individual mode, and cannot enlarge an existing NAS storage pool. This guide’s job is a separate backup destination, not extending the primary pool.

TerraMaster: four disks for your backup tools

The D4-320 keeps the enclosure side simple: each installed disk is presented individually. You can assign different backup jobs to separate volumes, or use host software for a more elaborate layout. TerraMaster explicitly documents third-party software RAID as the route to RAID; the enclosure itself supplies no RAID controller.

For separate backup jobs, give the volumes clear labels and record which job belongs on which disk. A versioned backup repository on each chosen destination is easier to operate when the job name, volume label and physical bay agree. Four anonymous disks are an excellent way to back up to the wrong place very efficiently.

If you want a host-managed array, choose the filesystem and RAID tool around the host’s support and your recovery plan. Don’t create a USB storage pool simply because all four disks appeared. Our RAID, snapshots and backups guide covers the layers that still need to exist around either enclosure.

RAID in the box or individual disks?

Pick the TR-004 when one RAID-backed destination fits your backup application. Pick the D4-320 when separate disks and separate jobs fit better.

A QNAP RAID group can keep running through a supported disk failure, while individual disks let each job target its own volume. Enclosure failure, filesystem support, encryption and the backup application’s catalogue still shape the restore path. QNAP specifically documents drive migration from one TR-004 to another TR-004; plan around that route rather than assuming a bare RAID member will open in any spare dock.

The dependable escape hatch is a file-level restore to another destination, using your backup software and saved credentials. Test that before the original NAS is the thing that needs replacing.

A sensible drive pairing

The registered WD Red Plus 8TB, WD80EFPX, is a CMR SATA drive option from the WD datasheet. Match the exact drive against your enclosure’s compatibility guidance; our NAS hard-drive guide covers the drive choice in detail.

As a worked capacity example, four equal 8TB drives give 32TB raw. A four-drive TR-004 RAID 5 group gives 24TB before formatting and metadata. In the D4-320’s independent layout, you have four separate 8TB disks, not one 32TB volume. QNAP requires the same disk type within a RAID group, so keep HDDs and SSDs in separate groups.

SMART access: use the documented route

QNAP’s External RAID Manager guide documents disk information and S.M.A.R.T. monitoring in its Windows/Mac utility. Supported QNAP NAS systems have their own management route. That is the health feature to buy around; a Linux host seeing the RAID volume is a separate capability from reading every member’s diagnostics.

TerraMaster’s specification marks built-in HDD S.M.A.R.T. Inspection as unavailable. Establish the host-tool route on your exact drive/enclosure combination before scheduling health scans. The upstream smartctl manual documents --scan-open for discovery and SAT device handling; our SMART-over-USB and SATA-dock guide walks through choosing the device type.

Keep health monitoring and backup verification as two jobs: one watches the disks, the other reads back the data you need to restore.

Fans, outages and the next scheduled backup

Both enclosures use an active 120mm fan. QNAP’s manual lists 18.1dB(A) in a low-speed, fully populated test within one metre. TerraMaster publishes below 21dB(A) in standby, with four SATA HDD/SSDs at one metre and a 17.3dB(A) test environment. Those are vendor test conditions; place the enclosure with room for rear airflow and listen during an actual backup, when the drives are seeking too.

Put the host and DAS on battery-backed power, using our UPS guide to size the combination. A host that stays on while its USB disks lose power still has an interrupted storage job.

If it must restart by itself after a power cut, ask the maker about that exact model; the desktop instructions don’t specify it. TerraMaster’s startup guidance explains that missing USB connectivity or drives can put the D4-320 into standby. Make drive recognition and mounting part of the recovery check.

After an outage, check power, drive/RAID status, mounts and job logs, then rerun verification and the interrupted backup as appropriate. For planned disconnection, stop the job and safely detach storage before switching off. QNAP specifies waiting at least two seconds between power-off and power-on.

Prove the backup with a restore

Use this acceptance checklist before trusting the schedule:

1. Record the layout. Save enclosure mode, bay/drive labels, filesystem, backup-tool configuration and encryption credentials somewhere outside the source NAS.
2. Run a small backup first. Include several file types, then change a test file and create another version so you can practise restoring an older copy.
3. Read the repository data. Use the backup tool’s integrity check, not just the job’s green tick. For restic, check --read-data reads the repository’s data packs as well as checking its structure.
4. Restore to an empty, separate destination. Choose a known snapshot and open the restored files. Compare content or checksums, then check permissions and filenames that matter to your workload.
5. Test a clean shutdown and restart. Safely unmount, shut down, restart and confirm the expected volumes return before the next job runs.
6. Test a missing destination. With the backup volume safely detached, confirm the scheduled job reports failure rather than silently writing into an ordinary folder on the NAS.
7. Keep another copy separate. Eject and disconnect an offline copy when appropriate, and keep your wider offsite plan. Four bays behind one USB cable still share an enclosure and power supply.

For an existing restic repository, these are the documented checks and restore shape. Replace SNAPSHOT_ID with an ID from the snapshot list and choose an empty restore directory:

restic -r /mnt/das-backup/restic snapshots
restic -r /mnt/das-backup/restic check --read-data
restic -r /mnt/das-backup/restic restore SNAPSHOT_ID --target /tmp/das-restore-test

The project documents local repositories and password requirements, integrity checks and restoring to a target directory. Save the password outside the machine being backed up.

Choose the enclosure for the job

TR-004 for enclosure-managed RAID; D4-320 for independent disks and the faster USB interface. Choose the destination layout first, then prove you can get a file back.

For a single fast NVMe drive, the USB4 enclosure guide is the better starting point. For occasional bare-drive inspection or cloning, use the SATA-dock guide. A DAS earns its desk space when you want several backup drives attached routinely—and a restore plan that works when you need it.