TerraMaster D4-320 DAS: Cheap Bulk Cold Storage That Actually Works
A four-bay USB enclosure with no network stack, no apps, and no RAID to argue with
Contents
Most of the storage hardware I write about here runs its own operating system — DSM, TrueNAS, OPNsense, something with a web UI and a login prompt. The TerraMaster D4-320 doesn’t. It’s a four-bay enclosure that connects over USB and shows up on whatever computer it’s plugged into exactly like any other external drive, no network share, no companion app, no server process running anywhere. That’s a much narrower proposition than a NAS, and for a specific job — bulk or cold storage attached directly to one machine — narrower is exactly what you want. Nothing here manages redundancy, serves files over a network, or has any opinion about your backup strategy — it’s four drive bays and a fast cable, and the rest is entirely up to whatever’s plugged in on the other end.
What a DAS is, and why that’s the point
Direct-Attached Storage skips the entire network-and-server layer that a NAS box builds its identity around. There’s no DSM-equivalent operating system to keep patched, no web interface to leave exposed on the network by accident, and no server process that can crash, need a reboot, or develop its own set of quirks independent of the drives themselves. The trade-off is equally direct: a DAS is only available to the one machine it’s physically plugged into, with no built-in way to share it across a network the way a NAS does natively. For content creators moving large files off cameras, for a single workstation that needs a big scratch volume, or for cold archival storage that only needs to be mounted occasionally, that trade is a good one — you’re not paying the complexity cost of a network file server for a job that never actually needed one.
Specs that matter for bulk storage
The D4-320 connects over USB 3.2 Gen 2, a 10Gbps link that’s a genuine step up from the USB 3.0/3.1 Gen 1 5Gbps connections most external enclosures still use. With all four bays populated, real-world sequential throughput reaches up to roughly 1,016MB/s, and even a single SSD installed alone can hit around 510MB/s read — numbers that put it comfortably ahead of a typical spinning-disk NAS on raw throughput, because there’s no network stack or filesystem-sharing protocol in the way eating into that bandwidth. Capacity-wise it supports drives up to 32TB each across the four bays, for a combined ceiling of 128TB, and takes 3.5-inch SATA HDDs or 2.5-inch SATA HDDs/SSDs interchangeably, so mixing a couple of large spinning drives with a fast SSD scratch disk in the same enclosure is entirely workable.
No RAID, and that’s a deliberate design choice
This is the detail that trips people up coming from NAS boxes: the D4-320 has no RAID controller at all. Each of the four bays presents as an independent disk to the host OS — plug it in and you get four separate drive letters or mount points, not one pooled volume. Any RAID or pooling you want has to happen in software on the host, using whatever your OS provides (Storage Spaces on Windows, a ZFS pool or mdadm array on Linux, an APFS or software RAID set on macOS), or you simply run it as JBOD and treat each bay as its own independent volume, which is the more common setup for exactly the cold-storage and bulk-transfer use cases this enclosure targets. It’s worth spelling out what that actually means day to day: there’s no rebuild to wait through if a drive fails, because there was never a RAID array to rebuild in the first place, only the one independent volume that drive was holding. That’s a real recovery-time advantage over a RAID array in a degraded state, and a real capacity-efficiency loss compared to one, since nothing here is protecting you from a single drive’s failure the way parity or mirroring would. For anyone specifically wanting hardware RAID with a web UI managing it, this isn’t that product, and TerraMaster doesn’t pretend otherwise — it’s marketed and priced as a JBOD enclosure from the outset.
Build details that show up in daily use
The tool-less push-lock drive trays let you swap a drive in seconds without hunting for a screwdriver, which matters more than it sounds for anyone regularly rotating drives in and out for offsite backup rotation. TerraMaster cut noise significantly compared to the previous generation of these enclosures through sound-absorbing panels and a smarter fan curve — idle noise sits around 21dB, genuinely quiet for a device with a fan and four spinning mechanical drives inside it, though obviously the actual noise floor of any specific build depends heavily on which drives you populate it with. Setup is properly plug-and-play: no driver installation required on any current OS, which fits the whole “no server, no software stack” philosophy the enclosure is built around.
Who this isn’t for
If the actual requirement is multiple devices on the network reading and writing the same shared folder, a DAS is the wrong shape for the job no matter how fast its USB link is — you’d be stuck sharing it manually from whichever single host it’s plugged into, reimplementing badly what a NAS already does natively. It’s also the wrong choice for anyone who wants hardware RAID with a management UI watching drive health and rebuilding automatically after a failure; that job genuinely needs a NAS’s onboard controller and software, not a JBOD enclosure that leaves every RAID decision to the host OS. The D4-320 earns its keep specifically when the job is single-host, high-throughput, low-complexity storage — stray outside that brief and the case for it weakens fast.
Setting it up for cold storage or bulk transfer
For cold storage specifically — drives you mount occasionally, copy to, and then leave powered down — the workflow is refreshingly simple compared to running a full NAS:
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For anyone wanting the four bays pooled rather than independent, a ZFS pool works fine over USB for a JBOD enclosure like this, with the caveat that USB-attached drives are less forgiving of a mid-transfer disconnect than a directly wired SATA connection — worth keeping backups of anything critical elsewhere regardless of the pool layout chosen, the same rule that applies to literally any single storage device or enclosure.
Troubleshooting
One bay doesn’t show up after plugging in. Confirm the specific drive is actually seated correctly in its tray — the tool-less push-lock trays are convenient but do occasionally need a firmer push than expected to make full contact, and a half-seated drive can appear to power on (activity light lit) without actually being recognised by the host controller.
Throughput is well under the rated figures. Check the actual cable and port in use — USB 3.2 Gen 2’s 10Gbps ceiling requires both a genuine USB 3.2 Gen 2 port on the host and a cable rated for it; plugging into an older USB 3.0 port, or using a cable bundled with a different, slower device, silently caps throughput well below what the enclosure itself is capable of.
A drive disconnects mid-transfer on a long copy. This is the most common real-world complaint with any USB-attached storage doing sustained large transfers, and it’s rarely the enclosure’s fault specifically — check the host’s USB power management settings first (the same autosuspend behaviour that affects USB network adapters affects USB storage), and consider a powered USB hub if the enclosure is sharing a bus with other high-draw devices.
Software RAID or a ZFS pool built on the enclosure behaves oddly after a reboot. USB-attached drives don’t always enumerate in the same device order after every reboot, which can confuse a naively configured mdadm array or mount table relying on device names like /dev/sda rather than stable identifiers. Building the array or fstab entries against UUIDs rather than device names avoids this entirely, and it’s worth doing from the start rather than after the first confusing reboot.
Enclosure fan runs louder than the quoted noise figure. The 21dB figure is measured at idle with the drives spun down or lightly loaded; four mechanical hard drives working simultaneously under sustained load will always be audibly louder than that idle figure, regardless of how quiet the enclosure’s own fan is — the drives themselves are usually the dominant noise source once they’re actually working. Populating it with 2.5-inch drives or SSDs rather than 3.5-inch mechanical drives sidesteps this almost entirely, at the cost of a lower capacity ceiling per bay.
DAS versus tape for genuine cold archives
For truly cold, rarely-touched archival storage — the backup you hope to never restore from — a spinning-disk DAS like this and LTO tape solve overlapping but distinct problems. Tape has a real edge on long-term unpowered shelf life and cost per terabyte at large scale, which is why it still shows up in serious archival strategies, including in a look at whether LTO tape is worth it at home in 2026. What a disk-based DAS offers instead is immediacy: plug it in and the data is there in seconds, with no tape drive to buy, no LTO cartridge handling discipline to maintain, and no specialist software required to read it back. For anyone whose cold storage genuinely means “months between touches, not years,” and who values being able to grab a file back without ceremony, the D4-320’s simplicity wins out over tape’s better cost-per-terabyte at the archive sizes most home users are actually dealing with.
Price and where it sits
Diskless, the D4-320 sits in roughly the $250-300 range, positioning it well below a comparable network-attached enclosure like a DIY NAS build or a low-end Synology box once you account for the fact that a DAS needs no separate compute for a server OS. That price makes sense once you remember what’s excluded: no CPU or RAM doing filesystem-sharing work, no software licence, no network stack to secure or maintain. Against a simple external drive doing the same one-bay job, the D4-320 costs more per bay, but the tool-less swappable trays and the ability to run four independent volumes or one pooled array from a single enclosure and a single cable is worth the premium for anyone who’s outgrown a drawer full of individual USB drives.
Where this fits against a real NAS
The honest comparison is against the specific job of getting a large amount of storage attached to one machine, cheaply and simply, without taking on the network-server complexity of a full NAS running its own OS. If the requirement genuinely is network-shared storage available to multiple devices, something like a Synology DS423 or a DIY N100 NAS build is the right tool, and a DAS is the wrong category entirely no matter how good the drive bays are. For everything else — a photographer or video editor’s working set, a backup target for one workstation, cold archival storage sitting mostly powered off — the D4-320’s combination of genuine USB 3.2 Gen 2 throughput, tool-less bays, and the complete absence of a server process to maintain is a strong, simple answer. Pair it with drives you trust — used enterprise SSDs off eBay are one option worth the research — and a good backup discipline elsewhere, and it does exactly the narrow job it’s built for without pretending to be anything more.
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