WD · Ultrastar HC550
WUH721816AL5205 is WD Ultrastar HC550 16TB SAS-12G. 2 of its 4 segments are defined in WD's published documentation and decoded below; for the rest we have not found a defining document, and they are marked as such. No live listings right now - the reference material below still applies.
| Segment | What it means | Source |
|---|---|---|
| WUH | Ultrastar DC HC series, helium-filled. | Western Digital |
| 721816 | Capacity and generation field. The leading digits encode capacity in the family's own scheme; each model's own specification sheet states its exact capacity. | Western Digital |
| AL | Not sourced - we have not found a WD document defining this segment. | Not sourced |
| 5205 | Not sourced - we have not found a WD document defining this segment. | Not sourced |
We decode only what the manufacturer documents. There is a large body of community knowledge about the undocumented segments above, much of it probably right, and none of it published by WD - so it does not appear in this table. A reading nobody can check does not belong in a column headed “what it means”. Grammar reference: Western Digital - Ultrastar model-number nomenclature.
WUH721816AL5205 is WD Ultrastar HC550, a 16TB hard drive on SAS-12G. Being a SAS device, it needs a SAS host bus adapter or backplane - it will not run from a motherboard SATA port, though a SATA drive will run on a SAS controller.
We hold no live listing against this exact part number at the moment. 1 sibling part number is documented below - these are the numbers most often mistaken for this one, and the table marks which fields actually differ.
| Manufacturer | WD |
| Family | Ultrastar HC550 |
| Capacity | 16TB |
| Interface | SAS-12G |
| Product class | HDD |
These are the part numbers most often confused with WUH721816AL5205. The differences below come from the same vendor documentation as the decode above - where a field is not documented, the row leaves it blank rather than guessing.
| Part number | Capacity | Interface | Format | |
|---|---|---|---|---|
| WUH722016CLE6L4 | SATA-6G | in catalogue |
Amber cells differ from WUH721816AL5205; grey cells match it.
No seller we track has WUH721816AL5205 in stock right now. That describes today's listings only - it says nothing about whether the model is discontinued. We are not going to fill this space with something else and call it a match. The decode, specifications and sibling table above are the reference answer for this part number and remain accurate whether or not anyone is selling one today. If you need the capacity rather than this specific part, the alternatives below are what is actually buyable.
A manufacturer part number does not imply a manufacturer warranty, and this is where part-number buyers lose the most money. OEM stock, integrator pulls and gray-market units all reach the market under the maker's own numbering. Retailers selling them sometimes state plainly that the manufacturer warranty is none; others simply do not mention it, which is not the same as it being covered.
Coverage attaches to the individual unit and its serial number, not to the part number. That means the only reliable answer comes from the manufacturer, about the specific drive you are being sold.
Ask the seller for the serial number and check it with WD directly before buying. We do not link a checker for this manufacturer because we have not verified one.
A seller warranty is a different promise from a different company. What each warranty tier actually covers · Verify on arrival
1 in-stock listing · same capacity and interface, any part number · ranked by live cost per tb, refreshed about once a day
| Drive | Capacity | Interface | Recording | Condition | $/TB | Price | |
|---|---|---|---|---|---|---|---|
| Seagate Exos 16TB SAS 12G 7.2K ST16000NM002G | 16TB | SAS-12G | — | REFURB This offer: sold by Redefine IT · Amazon says New / New · title says Renewed | $34.28 | $549 | Buy/View Price |
Every 16TB drive we track, ranked by cost per terabyte.
WUH721816AL5205 is WD Ultrastar HC550 16TB SAS-12G. 2 of its 4 segments are defined in WD's own published documentation - the decode table on this page shows each one with the document that defines it. For the remaining segments we have not found a defining document, and we say so rather than repeating a community guess as fact.
Not necessarily, and the part number cannot tell you. Coverage depends on how the individual unit entered the market and whether it was registered, not on its model designation. OEM and gray-market stock reaches the market under manufacturer part numbers regularly and frequently carries no manufacturer warranty at all - some retailers print exactly that on the listing. Check the specific serial with the manufacturer before buying.
Both are in the Ultrastar HC550 range. They differ in interface: SAS-12G against SATA-6G, which decides whether the drive fits your controller. The variant table on this page lists every sibling we document with what differs.
We hold no live listing for this part number right now. That is the honest state rather than a broken page - this remains the reference answer for what WUH721816AL5205 is, how it decodes and which siblings it is confused with. The alternatives section below shows what is currently buyable at the same capacity.
Because more than one organisation names it. The manufacturer assigns a model number describing the product; a server vendor buying it in volume assigns its own spare-part number for its service catalogue; distributors sometimes add another. All identify the same physical drive, which is why one number returns listings that look like a different product. Our part number index explains the pattern per vendor.