Shucking WD and Seagate External HDDs: What’s Inside the Enclosures

Armchair Analysis

Let’s be honest: it’s hard to believe HDD makers WD and Seagate don’t know their margins and are selling good hardware for much less—sometimes half the price. You should only take advantage of that if you know in advance exactly what’s inside the enclosure. Manufacturers have no interest in cannibalizing the more profitable bare-drive sales and, with rare exceptions (which we’ll discuss later), won’t tell you exactly which model is inside.

Moreover, the same external drive model — for example, a WD Elements Desktop — can come with completely different internal drives, not only in capacity but also in other parameters that aren’t publicly disclosed. Hoped to get a WD Red but found a WD Blue inside? Sorry, that’s a weak basis for a return. Okay with a WD Blue, but received a mysterious white‑label drive? That’s not always a problem, but there are important nuances to be aware of.

It might seem the obvious way to learn what’s inside a given model is to Google it. Chances are the top results will be Reddit threads. But the first thing I’ll ask you to do is forget, for a minute, whatever you’ve read on Reddit about external drives. Different production runs of external enclosures can ship with different drive models, and the fact that some anonymous user ended up with a particular drive doesn’t mean you’ll get the same—or even a similar—one. What’s more, Reddit is full of myths that get repeated year after year. We’ll talk about those too.

Brave New World

A couple of years ago it was simple: Western Digital external drives up to and including 6 TB were air-filled (atmospheric), used true CMR recording, and spun at 5400 RPM. Models 8 TB and up also used CMR, but the enclosures were helium-filled and the spindle speed was 7200 RPM. The “5400 RPM performance class” label is confusing—it doesn’t reflect the actual spindle speed, it’s just a marketing performance tier and another way to sell the same thing with a different sticker. Today the lineup has gotten muddier: there are SMR variants (at 2 TB and 6 TB—I’ve personally run into one), and there are 8 TB atmospheric models that run hotter and louder than their helium-filled counterparts.

The situation with Seagate external drives has also become ambiguous. Not long ago, it was common knowledge that Seagate externals—regardless of capacity—used SMR (shingled magnetic recording). Without TRIM support, rewrite speeds would nosedive as soon as the cache filled after the first full pass. Buying them to shuck wasn’t worthwhile—the price difference versus WD made the whole idea pointless. Today, however, the lineup includes at least two 10 TB models that house an excellent helium-filled CMR drive spinning at 7200 RPM, whose performance is being choked by a very basic USB controller (I’ll cover this in more detail in the relevant section). Shucking such a drive unlocks its potential. I did exactly that and recorded HD Tune performance graphs that clearly demonstrate throttling at the USB controller level.

Who’s the manufacturer?

There are only three major hard drive manufacturers left: Seagate, Toshiba, and Western Digital. In the consumer market, though, only Seagate and WD have broad, mainstream offerings; you can find a Toshiba drive if you really want to, but there isn’t much reason to. External drives, on the other hand, are sold both by the two big players and by a long list of smaller brands. Companies like Transcend, Verbatim, Intenso, and many regional labels buy bare drives from one of the manufacturers, put them into external enclosures, and sell them with their own warranty and support. With first-tier manufacturers, the warranty and service are handled by the brand that actually made the drive.

First up is Western Digital, which sells external drives under the WD name and the “premium” G-Drive brand. Inside these enclosures you’ll typically find WD or HGST (Hitachi) hard drives; HGST has been part of Western Digital since 2012. Many buyers consider it a win if they happen to get an HGST unit. In most cases, rebranded helium-filled HGST drives show up in WD My Book and WD Elements models with capacities of 8 TB and higher. Lower-capacity models usually come with WD’s own drives. If you don’t want to roll the dice and would rather get a true HGST without the rebranding shuffle, the manufacturer has you covered: the 8 TB and 12 TB WD_BLACK D10 models are built with Ultrastar-series drives.

Western Digital’s closest competitor is Seagate, which also offers drives under its own brand and under the “premium” LaCie label. And while Seagate-branded drives are straightforward (what else did you expect to find there?), LaCie raises some questions.

Back in the day, LaCie was an independent company. Its external drives could ship with just about any internal HDD (our lab’s teardown unit, for example, had a Hitachi drive, a brand that later became part of WD). In 2014, Seagate acquired LaCie, and since then LaCie external drives have been, or are supposed to be, fitted exclusively with Seagate disks. Hallmarks of the LaCie lineup include Thunderbolt support and a reversible USB Type‑C port. Multi‑bay LaCie enclosures typically use Seagate IronWolf Pro drives, while single‑drive LaCie and Seagate models come with Seagate Barracuda drives.

WD vs. Seagate?

So, we’ve settled on the manufacturers. We’ll exclude the G-Drive and LaCie lines from consideration: buying external drives under those brands just to harvest the internal disks isn’t cost-effective. With WD and Seagate externals, though, the idea can make sense.

So which should you choose: Seagate or Western Digital? Setting aside personal preferences and brand reputations (both have had their hits and misses), the internals of their external drives are markedly different. Let’s go in alphabetical order.

Seagate External Drives

The company offers two primary 3.5-inch external drive families: Seagate Expansion Desktop and Backup Plus Hub.

The product lines differ in enclosure design, feature set (the Backup Plus Hub has a built-in two-port USB hub), and in some countries—bonus extras like a two-month Adobe Creative Cloud subscription. Inside, drives of the same capacity use identical hard disk models. If you don’t need the Adobe CC subscription and plan to remove the drive from the enclosure anyway, it makes sense to buy the cheaper option.

What’s inside?

A while back you could still run into Seagate Desktop models, but in today’s Expansion Desktop and Backup Plus Hub external drives you’ll most commonly find disks from the Seagate Archive or Seagate Barracuda families. The latter come in two variants: Barracuda Compute (up to and including 8 TB; 5900 RPM, air-filled, using SMR shingled recording) and Barracuda Pro (currently available as externals only in 10 TB; helium-filled, 7200 RPM, using CMR conventional recording).

For the 6 TB version, you typically get one of two drives: ST6000AS0002 or ST6000DM004. The 8 TB version often ships with ST8000AS0002 or ST8000DM004. For example, the Seagate Expansion Desktop 8TB unit received in March 2020 came with a Barracuda Compute ST8000DM004-2CX1 inside—noticeably hot and noisy.

When you buy an external drive, it’s important to understand where exactly Seagate is cutting costs. IronWolf drives use conventional magnetic recording (CMR), while the Archive and BarraCuda Compute models found in units up to and including 8 TB use shingled magnetic recording (SMR).

So, we’ve covered Seagate’s Expansion Desktop and Backup Plus Hub external drives up to and including 8 TB. If I’d written this a year to a year and a half ago, I would’ve put a hard stop here and ruled out Seagate externals as donors for internal HDDs. But things have changed: trying to keep pace with its main competitor—which already had 10, 12, and 14 TB externals—Seagate decided to launch a 10 TB external drive. Given how far behind WD it was in high-capacity externals, Seagate chose to postpone a cost-reduced 10 TB SMR model. To hit the market faster, they used what was already available: a lineup of three 10 TB drives—Barracuda Pro, IronWolf, and SkyHawk. As a result, the Seagate Expansion Desktop 10TB and Backup Plus Hub 10TB ended up shipping with the excellent Barracuda Pro 10TB, model ST10000DM0004.

I bought a 10TB Backup Plus Hub drive and tested it with HD Tune. The results were interesting.

As you can see, the cheap USB controller built into the external enclosure can’t handle the data rate, capping the transfer speed at 175 MB/s. We remove the drive and put it into a higher-quality enclosure (QNAP TR-002).

We’re now seeing a more familiar chart, with a maximum read speed of 225 MB/s on the outer tracks.

I find the Barracuda Pro 10TB drives to be an excellent choice: quiet both at idle and during random read/write, fast, and running fairly cool—especially compared to the 6TB and 8TB models. They’re definitely worth the money.

An interesting wrinkle: Seagate sells completely different drives under the same name and even the same model identifier. The suffix of the model (what Seagate calls the part number) changes—and so do the specs. For example, in Backup Plus Hub external drives I’ve come across ST10000DM0004-1ZC101 and ST10000DM0004-2GR11L. They differ both in performance (the latter is faster) and in their S.M.A.R.T. attribute set (the older unit exposes attributes like G-Sense Error Rate, while the newer one has that and many others removed from diagnostics). The S.M.A.R.T. data format also differs: the older model appears to report power-on hours in seconds, while the newer one reports them in hours. The newer variant also showed lower vibration—though that could just be unit-to-unit variance. However, the performance graphs diverge so much that variance alone can’t explain it.

The Money Question

The savings are obvious. A standalone Seagate Barracuda Pro 10TB runs about €290. A Seagate Backup Plus Hub 10TB—containing the exact same drive—sells for €190. A deal? Definitely. But for some, it’s also a way to run a rather questionable business. Dozens of sellers on Amazon and eBay offer ST10000DM0004 drives at very attractive prices. Buyers tempted by the low price receive a brand-new drive in OEM packaging, but a warranty check on Seagate’s site by serial number returns a denial: the drive was intended for sale only as part of an external enclosure. Savvy resellers simply tore down batches of external drives, pulled the disks, and decided to cash in. In some cases, buyers managed to return these drives to the seller, but I wouldn’t count on those sellers honoring any warranty.

The only real reason to buy the bare drive is the warranty. Seagate gives the standalone drive a five-year warranty, but only two years if it comes in an enclosure. Whether saving 30% is worth losing those extra three years of coverage is up to you.

Why take them apart?

Are there good reasons to shuck Seagate external drives and pull out the bare drives? Yes—even if you set aside the price difference between a drive in an enclosure and a standalone bare drive.

Seagate enclosures are poorly designed. They have almost no ventilation: the only openings are at the bottom. The honeycomb pattern you see on the top of the Seagate Backup Plus Hub is purely cosmetic—the top cover is solid. As a result, air-filled drives (especially the 6 TB and 8 TB models) overheat quickly. During extended writes—and writes to an SMR drive take a long time—I saw temperatures reach 61°C. That’s not healthy for hard drives.

Seagate uses the cheapest USB controllers, which bottleneck data transfer speeds. I’ve shared comparative speed graphs of the same 10 TB drive in a Seagate enclosure and, after shucking, in a different external enclosure. The difference is obvious.

Finally, the USB controller firmware in Seagate Backup Plus models has bugs that cause certain features to be disabled on Linux (notably UAS — USB Attached SCSI), which further hurts performance. More details are in this Reddit post. Even if you don’t use Linux directly, you might want to use the drive as a backup disk for a NAS, which almost certainly runs Linux. According to some reports, the issues are fixed in the Seagate Backup Plus Hub, but the Linux kernel still blacklists UAS for these devices as a precaution.

Why You Probably Shouldn’t Do It

What should you consider before picking up a screwdriver?

Once you crack open the enclosure, you automatically void the warranty. With WD Elements Desktop or WD My Book, you can usually open and reassemble them without damage (WD is fairly lenient about this and typically won’t refuse warranty service). Seagate enclosures, however, are essentially single-use: the plastic clips usually break during disassembly. That’s almost certainly by design. So if you ever need warranty service, you probably won’t be able to pop the drive back in and pretend nothing happened. I don’t have any other arguments against taking apart Seagate external drives.

How to take it apart

There are plenty of guides online that show how to open external enclosures and remove the drives.

If you want, you can easily find a dozen or two alternative guides, including from Russian-speaking users. I found the guide by an iFixit user and the write-up on mattgadient.com helpful.

Western Digital External Hard Drives

Western Digital offers several lines of 3.5-inch external drives. These include the WD Elements Desktop, WD My Book, WD My Book Duo, and WD_BLACK D10. Let’s sort out the differences, but first—a quick summary.

WD Elements Desktop

• Warranty: 2 years
• Warranty applies to: the entire external unit (enclosure + drive)
• What’s inside: mostly White Label (EMAZ) drives
• Built-in (hardware) encryption: none
• Access to previously written data after removing from the enclosure: yes
• Enclosure opening difficulty: moderate
• Cost per terabyte: lowest among the options
• Notes: possible issues with the 3.3 V pin on the SATA power connector (see this guide)

WD My Book

• Warranty: 3 years
• Coverage: the entire external unit (complete drive assembly)
• What’s inside: mostly White Label (EZAZ) drives
• Built-in encryption: yes, drive-level (SED)
• Access to existing data after removing the drive from the enclosure: yes, if no password was set; no, if a password was set
• Enclosure opening difficulty: moderate
• Price per terabyte: slightly higher than Elements, but lower than WD My Book Duo
• Notes: potential issues with the 3.3 V power pin on the SATA power connector (https://www.instructables.com/id/How-to-Fix-the-33V-Pin-Issue-in-White-Label-Disks/)

WD My Book Duo

• Warranty: 3 years
• Warranty coverage: applies to each drive individually; no different from the warranty for WD Red drives purchased separately
• What’s inside: two WD Red drives. Note: the WD My Book Duo 12TB ships with two 6 TB drives.
• Built-in encryption: yes, implemented in the USB controller; a password can be set only in RAID 0 or RAID 1 (not JBOD); regardless, hardware encryption of written data is always on.
• Access to previously written data after removing the drives from the enclosure: no (unless you use another enclosure of the exact same model). After removing the drives from a My Book Duo, you cannot read the data directly (or in a different-model enclosure). In another WD My Book Duo enclosure of the same model, the data is accessible normally.
• Enclosure opening difficulty: low; the drives are easy to remove using the standard procedure.
• Price per terabyte: slightly higher than WD My Book.
• Notes: see the encryption remarks above.

WD_BLACK D10

• Warranty: 3 years
• Warranty covers: the complete unit (drive in its enclosure)
• What’s inside: genuine, non-rebadged Ultrastar DC drives — 8 TB (air-filled) or 12 TB (helium-filled)
• Built-in encryption: none
• Access to previously written data after removing the drive from the enclosure: yes
• Enclosure opening difficulty: higher than average
• Price per terabyte: the highest among these options, but still far below the cost of buying Ultrastar DC drives bare
• Notes: the drives are fairly noisy. Do you even need to shuck them? The enclosures are well made, high-performance, with active cooling.

WD Elements Desktop

WD Elements Desktop, also sold as WD Easystore (a Best Buy exclusive), sits at the entry level of WD’s external drive lineup. Its strengths include a well-designed enclosure that can be opened non-destructively with a bit of care, and a solid USB controller that doesn’t bottleneck performance or force hardware encryption. You can use Elements Desktop drives straight out of the box: WD has done a good job with noise and vibration damping and thermal management, with ventilation grilles on both the top and bottom of the enclosure.

In recent years, WD Elements Desktop units have shipped exclusively with WD White Label drives (earlier batches could include WD Blue in models up to 6 TB and WD Red in 8 TB versions). In models up to and including 6 TB you’re guaranteed to get an air‑filled drive with a 5400 RPM spindle speed. For example, in a 4 TB unit I found a WD40EMRX-82UZONO (White Label, CMR).

The 6 TB model is a special case. As recently as last year, these units shipped with CMR drives, but the ones purchased this spring turned out to have WD60EMAZ drives (white-label, SMR shingled recording with TRIM support). You can use these drives individually, but I wouldn’t put them in a RAID array.

Finally, the 8 TB and larger models use helium‑filled CMR drives with a 7,200 RPM spindle. Despite that, they’re marketed as “5400 RPM Class,” which seems more like Western Digital’s product segmentation than a reflection of the actual spindle speed. All of these models are essentially hardware clones of HGST/Western Digital Ultrastar DC drives from various generations.

WD drives up to and including 6 TB run cool and quiet, and generally aren’t prone to vibration. The 8 TB models (recent WD80EMAZ revisions) are quiet on their own but can vibrate noticeably. Western Digital’s quality control for drives supplied in external enclosures leaves something to be desired: I’ve come across units with barely perceptible vibration and others that vibrate quite a lot.

Not long ago, that might have been the end of the story, but Western Digital keeps surprising users. For example, one Reddit user, expecting the tried‑and‑true helium‑filled WD80EMAZ, ended up with the same WD80EMAZ model—but air‑filled (non‑helium).

As it turns out, this model is part of a new generation of drives built on the Ultrastar DC HC320 platform.

As of today, the largest WD Elements Desktop capacity is 14 TB. Inside you’ll find this drive. In practice, the enclosure contains a rebranded WD Ultrastar DC HC530 7200‑RPM SATA made by HGST. The label’s FCC Regulatory Approval Number US7SAP140 lets you positively identify it as an HGST Ultrastar DC HC530.

How to Open the Enclosure

Opening the WD Elements enclosure is relatively straightforward. Press the plastic clips on the top and bottom of the case, then carefully slide off the protective cover. With a bit of care, you can do this without damage. Instructions are in the video.

WD My Book

WD My Book drives sit one tier up in Western Digital’s external lineup. Compared to the Elements Desktop models, they use a different enclosure design, omit the LED indicator, and include built‑in AES‑256 encryption (apparently implemented on the drive itself).

According to the WD External Drive Hardware Encryption Compatibility Matrix, data on drives removed from a WD My Book can be read even without the enclosure, provided no password was set. This suggests the encryption isn’t handled by the USB controller (as it is in dual-drive models), but at the drive level via SED.

Is there any performance difference between EMAZ (WD Elements Desktop) and EZAZ (WD My Book) drives? Users say that if there is, it’s minimal.

Otherwise, there’s little to set it apart from the Elements models. The differences are a different enclosure design, a slightly different (some say even simpler) disassembly method, a three-year warranty, no LED indicator, and built-in encryption (likely SED). Inside, My Book units use the familiar White Label drives, which are hardware-equivalent to the corresponding WD Blue or Ultrastar DC models.

How to take it apart

Opening the WD My Book enclosure is fairly straightforward. Just release the plastic clips located along the bottom of the drive. Many video guides suggest popping the clips at the top as well, but that isn’t necessary. Note: once the clips are released, the inner assembly can unexpectedly slide out of the shell, so it’s wise to put something soft on the table beforehand. Here are the instructions.

WD My Book Duo

WD My Book Duo two‑bay models are notable because you can easily remove and replace the drives, which are standard WD Red units. Western Digital’s warranty applies both to the complete enclosure and to each drive individually (note: store policies may vary, so it’s best to register the device on WD’s website right after purchase and verify that the warranty is set up correctly).

Dual-drive WD My Book Duo models are often priced lower than buying two WD Red drives separately. With a three-year warranty that lets you replace either drive, picking up a My Book Duo is the safest way to get a pair of WD Red drives.

If you plan to use the drives in the original enclosure, note that the USB controller enforces always-on encryption. Even if you don’t set a password, everything written to the device is encrypted and can only be read in an identical enclosure. The original capacity doesn’t matter: for example, WD My Book Duo 12 TB enclosures work fine with drives pulled from WD My Book Duo 16 TB units, and vice versa. That said, if you’re going to install the drive in a NAS, the data will be lost during array initialization anyway.

WD_BLACK D10

The WD_BLACK D10 drives give me mixed feelings. On the one hand, they’re practical, use active cooling (a small, quiet fan), and look great—it almost feels wrong to take them apart. On the other hand, they contain Ultrastar DC HC320 disks known for high performance and reliability, but also relatively high noise. And third, the 8 TB model is air-filled—so it’s comparatively noisy and runs hotter—while the helium-filled counterparts in WD Elements and My Book look more appealing and cost less.

There’s nothing particularly distinctive about these drives, except that they still use the long‑outdated USB 3.0 Micro‑B connector instead of a symmetrical USB‑C, which would make more sense for a drive in this class. No built‑in encryption.

Disassembly

Disassembly is trickier than it looks: besides screws, the top cover is also held by plastic clips, and releasing them without damage is a bit harder than on the models we looked at earlier.

These drives are fairly new, so there aren’t many disassembly guides yet. The most sensible one to date is in German.

Helium or Shingled (SMR)?

We now have a clear picture of what drives manufacturers put into external hard drives. The only models that don’t raise concerns are air-filled 5400 RPM drives using CMR recording. However, Seagate doesn’t use those in its external lineup at all, and Western Digital is gradually phasing them out, replacing the entry-level models with shingled (SMR) drives.

Both companies use helium-filled drives in their external storage lines. For Western Digital, that covers all models 10 TB and up, as well as (as of today) the vast majority of 8 TB units. For Seagate, helium starts at 10 TB.

Helium-filled HDDs offer a number of advantages—quieter operation, lower power consumption, the ability to stack more platters, and so on. Still, some users worry the helium will eventually seep through the metal lattice and escape into the atmosphere. Since helium drives are relatively new, it’s hard to dismiss those concerns outright. So which necessary evil would you rather choose—helium or shingled recording (SMR)?

When it comes to Seagate drives, there isn’t much to debate: you’re basically choosing between the company’s cheapest—in the not-so-good sense—models up to and including 8 TB, and some of the most technically advanced ones (10 TB, plus the recently introduced 12 TB and 14 TB). These are entirely different product lines with a huge gap between them.

Western Digital is a bit trickier. Their air-filled WD drives up to and including 6 TB are virtually silent, with exceptionally low power draw and heat output. For the 6 TB model specifically, the SMR version that replaced the CMR drive runs even quieter and cooler. Thanks to TRIM support, you won’t notice much performance difference between the CMR and SMR models—unless you try to use the drive in a RAID 5 array or with ZFS.

8 TB drives (if you happen to get a helium-filled unit) and 10–14 TB models typically spin at 7200 RPM. On paper, their acoustic levels are allowed to be fairly high, but in practice many users don’t hear so much motor noise as a low hum caused by the drive’s vibration coupling into whatever surface it’s mounted on. With a single drive you can often mitigate that hum, but two helium drives in a standard 2‑bay NAS will vibrate more than two 5400 RPM drives.

When 5400 RPM Is Really 7200 RPM

So why do I claim WD’s helium drives actually spin at 7200 RPM when the spec sheet clearly says 5400 RPM? This looks like a neat case of reverse marketing: the company intentionally understates a key spec so it can sell the same mechanics—possibly with tighter QA, different firmware, or even a different controller—at a higher price under the WD Red Pro or Ultrastar DC brands.

One common myth about WD’s helium-filled models stems from drive labeling and what S.M.A.R.T. reports. Many users believe WD White Label drives are simply rebadged HGST units with their spindle speed throttled from 7200 to 5400 RPM. Frankly, it’s hard to imagine you can just dial down a drive’s spindle speed without a major redesign of its components; plus, I haven’t personally seen any helium-filled drives running that slow. But S.M.A.R.T. says otherwise. Take a look at the screenshot showing the specs of a WD Red installed in a WD My Book Duo enclosure.

It seems obvious: the spindle speed is 5,400 RPM. What’s there to think about? If you don’t believe it, you can check the specs on WD’s website.

It’s stated in black and white: “spindle speed — 5400 RPM.” For the skeptics, the official specifications are available.

So it’s 5400, right? Almost. Watch closely. The official specs don’t say a word about spindle speed. Instead, they use a “performance class,” labeled “5400 RPM Class.” Here’s the kicker: every helium‑filled hard drive (which is most models 8 TB and up) actually spins at 7,200 RPM. The physical RPM is 7,200, but the marketed performance class is 5400 RPM. Don’t confuse the two.

So why does WD downplay the specs by labeling the drives as “5400 RPM Class” and even state 5400 RPM as the spindle speed on the product page? That little marketing fib lets the company segment the market, nudging performance‑minded buyers toward the pricier WD Red Pro line or even more expensive HGST enterprise drives. In reality, the 5400 RPM Class includes both true 5400 RPM models (all air‑filled drives up to and including 6 TB, plus a few rare 8 TB air‑filled models) and 7200 RPM models (all helium‑filled drives from 8 TB and up).

A fair question: why should you trust me over the hive mind, Reddit posts, S.M.A.R.T. readouts, or the specs on the product page? You don’t have to take my word for it—you can easily measure the spindle speed yourself. All you need is any Android phone and the free Spectroid app.

Taking the measurement is straightforward. Start the app and hold your phone close to the running drive. The app will analyze the audio spectrum and show you the frequency or frequencies where a peak is detected.

As we can see, the WD Red 8TB shows a peak at 120 Hz. Multiply 120 by 60 and you get 7,200 RPM, which matches the spindle speed.

The Mystery of WD White Label Drives

There’s a lot of speculation online about what the white‑label Western Digital drives inside external enclosures really are. With air-filled models it’s more or less clear: they’re hardware clones of WD Blue drives of the same capacity. Helium-filled units are a different story. It’s hard to doubt that WD reuses the same hardware platform across multiple lines—from HGST Ultrastar DC, WD Red Pro, WD Red, and WD Purple to the “white label” drives found in plastic external enclosures. Even on the same platform, Ultrastar DC and WD Red Pro tend to be louder and faster than WD Red and the white-label models (which are practically identical to each other). What might explain that?

Here we’re treading on thin ice of rumors and speculation. On the one hand, consumer drives may use the exact same mechanical platform as their pricier counterparts. Evidence for this comes from unique Regulatory Number identifiers assigned by government product certification bodies. If drives with different branding (and different model identifiers) share the same Regulatory Number, they’re the same hardware at the physical level. A far-from-complete mapping of model numbers to Regulatory Numbers is provided below (source): source

• WD80PURX = R/N US7SAJ800
• WD81PURZ = R/N US7SAN8T0
• WD80EMAZ = R/N US7SAL080
• WD80EZAZ = R/N US7SAL080
• WD80EZZX = R/N US7SAJ800
• WD80EFAX-68KNB0 = R/N US7SAN8T0 (air-filled model based on the Ultrastar DC HC320 platform)
• WD80EFAX-68LHPN0 = R/N US7SAL080 (helium-filled model based on the Ultrastar DC HC510 platform)
• WD80EFZX = R/N US7SAJ800
• WD100EMAZ = R/N US7SAL100
• WD101PURZ = R/N US7SAL100
• WD101KRYZ = R/N US7SAL100
• WD120EDAZ = R/N US7SAM120
• WD120EFAX = R/N US7SAM120
• WD120EFMZ = R/N US7ASP140
• WD120EMAZ = R/N US7SAM120
• WD121KRYZ = R/N US7SAM120
• WD121PURZ = R/N US7SAM120

By the corresponding regulatory model number (R/N), it’s easy to determine a suitable donor model. For example, the popular current WD80EZAZ shucked from a WD My Book enclosure with R/N US7SAL080 is built on the Ultrastar He10-8 SATA platform, which was later rebranded as Ultrastar DC HC310. An older WD80EZZX has R/N US7SAJ800, identifying it as the Ultrastar He8-8 SATA platform—a less attractive option.

Note the line WD120EFMZ = R/N US7ASP140. There are several 12 TB WD external drive models on the market. Interestingly, some of them use the same drives that ship in the 14 TB models—firmware-locked to 12 TB. Most likely, these drives didn’t make the cut for the higher-capacity bin and were repurposed by the company accordingly.

So why are performance and noise levels so different? At this point we can only speculate. One theory is QC binning: the best drives ship under the Ultrastar label, the next tier goes to the budget WD Red lines, and the slightly worse ones are put into external enclosures. The problem with this theory is that external drives outsell all other disk categories by a wide margin—by multiples, if not an order of magnitude. Does WD really have a defect rate that high? Highly doubtful.

Another theory: WD is putting refurbished drives into its external products. But then again—where would the company get that many refurbs, especially given how hard helium‑filled models are to repair?

Personally, I find more convincing the theory that involves binning during quality control, with drives made quieter (and slower) through firmware tuning, in a way similar to the now-retired Automatic Acoustic Management (AAM) system.

The Mysterious WD80EFAX

In the table above you may have noticed two different drives with the same model prefix: WD80EFAX-68KNB0 and WD80EFAX-68LHPN0. These are two variants of the WD Red 8TB. When you buy this model (and also a drive in an external enclosure, like a shucked WD80EMAZ), you can end up with either a helium-filled 7‑platter unit based on the Ultrastar DC HC510 platform (formerly He10), or an air‑filled 5‑platter unit based on the Ultrastar DC HC320 platform. You can often tell them apart by their exterior, but if the drive is inside an enclosure and you don’t want to open it, check for S.M.A.R.T. attribute 22 — Helium Level (initially 100). If attribute 22 is present, it’s a helium drive; if it’s absent, it’s an air drive.

Which option to choose? The air-filled model runs hotter and noisier, but it’s unclear which one will be more reliable in the long term. The air version is cheaper to manufacture (fewer platters, vented design).

Bottom line

An external drive is a pig in a poke, and buying one is a lottery. In this article, I try to shed some light on what you might actually find inside that plastic enclosure. I hope this helps you make an informed decision.