Brands we trade
WD Ultrastar and HGST: One Company, Three Labels
GTR Supply buys and sells Western Digital Ultrastar enterprise drives by the lot, and this page exists to answer the question a pallet of them always raises: why do the labels say three different companies. Western Digital acquired HGST in 2012 and SanDisk in 2016, and the part numbering from all three lineages is still live. An HUH or HUS number is an HGST heritage part and it is a current Western Digital enterprise drive. An SDLF number is a SanDisk heritage part in exactly the same way. So a pallet that looks like three brands is one, and listing it as three makes the lot look more mixed than it is. This page shows you how to read each prefix and, more importantly, the one letter that tells you whether a drive uses shingled recording. Every part number here is identification help for the reader, never a stock listing. Send the part numbers with counts and we will tell you where we stand.
How to identify it
Work out what you have.
Where the identifying number physically sits, how to read each field in it, and what it tells a buyer. Useful whether or not you ever trade anything with us.
Three labels, one company, and why the old numbers are still live
Western Digital acquired HGST, itself formed from Hitachi and IBM's storage businesses, in 2012, and acquired SanDisk in 2016. Product lines were not thrown away at either point. They were renumbered gradually, and the older prefixes stayed in production for years afterwards.
The result is that a single enterprise drive family can appear under three different looking part numbers depending on when the drive was made. An HUH number is an HGST heritage helium filled drive. An HUS number is the HGST heritage air filled line. WUH and WUS are the Western Digital numbers that succeeded them and describe the same kinds of drive. SDLF and similar prefixes are SanDisk heritage numbers on enterprise flash.
The flash side has changed hands and branding more than once since, so an Ultrastar DC SN drive may carry a Western Digital or a SanDisk label.
None of this is a fault or a grey market question. It is a naming history, and knowing it stops a seller from splitting one family into three lines on a manifest.
Reading an Ultrastar part number, and the one letter that matters most
Ultrastar hard drive part numbers pack the interface and the sector format into a short letter group in the middle of the string, and it is the most useful field on the label.
The pattern is consistent. An ALE group means a SATA drive using 512 byte emulation. ALN means a SATA drive using native 4K sectors. AL5 means a SAS drive using 512 byte emulation and AL4 means a SAS drive using native 4K. The capacity sits in the digits before it and the rotational speed in the digits before that.
The prefix carries the single most important fact on the label. HUH, HUS, WUH and WUS drives use conventional recording. Prefixes carrying an S in that position, HSH and WSH, are shingled magnetic recording drives, where tracks overlap to increase density. Shingled drives are excellent for sequential and archival work and behave very differently under sustained random writing, which is why putting one into a general purpose array causes trouble that looks like a fault and is not.
Write the prefix down exactly. It is four characters and it changes everything.
DC HC, DC HA and DC SN: what the letters after DC mean
Modern Ultrastar drives carry a marketing name alongside the part number, in the form of DC and then two letters and a number, and the two letters tell you which kind of device you are holding.
DC HC is the high capacity 3.5 inch nearline line, which is the bulk of what comes out of a storage refresh. The number rises with the generation, so the 500 series and the 600 series sit on either side of a significant capacity step, and the 600 series is where the shingled parts live.
DC HA is the smaller air filled 3.5 inch nearline line, built for lower capacities than the helium filled drives.
DC SN is the NVMe solid state line and DC SS is the SAS solid state line, so a DC SN part is not a hard drive at all despite sitting in the same naming scheme.
One more label is worth knowing. WD Gold is the retail channel version of the enterprise platform, so a WD Gold part number and an Ultrastar part number can describe closely related drives with different packaging and different channels behind them.
What is in circulation
The families you will meet.
Placing your hardware in the right family does most of the work of describing it. Each note below says what separates that family from the one above it.
Ultrastar DC HC
The high capacity helium filled 3.5 inch nearline line, and the bulk of what comes out of storage refreshes. Numbered by generation across the 500 and 600 series.
Ultrastar DC HA
The air filled 3.5 inch nearline line at lower capacities. Same market as DC HC, different construction, and a different capacity band.
Shingled recording drives
The HSH and WSH prefixed parts, where tracks overlap to raise density. Excellent for archival and sequential work and a poor fit for random write arrays.
Ultrastar DC SN NVMe flash
The NVMe solid state line in U.2, U.3 and add in card forms. Not a hard drive despite the shared naming scheme, and priced on a completely different basis.
Ultrastar DC SS SAS flash
The SAS solid state line, sold into arrays and servers that expect a SAS backplane. Includes drives that carry SanDisk heritage numbering.
Ultrastar C10K and C15K
The 2.5 inch mission critical SAS spinning drives at ten and fifteen thousand revolutions. A performance market rather than a capacity one.
HGST heritage numbers
HUH, HUS, HUSMM and HUSMR parts. Live Western Digital enterprise drives under the previous company's numbering, not obsolete or grey stock.
SanDisk heritage numbers
SDLF and similar prefixes on enterprise flash, from the CloudSpeed, Lightning and Optimus lineages. Still in circulation and still identifiable.
The same categories, every manufacturer
The families above are this manufacturer's own lines. The category pages carry the wider list, everything that circulates in each category whoever built it, with the part number prefix or physical marker that identifies each one. They are identification help rather than stock lists.
None of this is a stock list
Every model name and part number on this page is identification help for the reader. None of it is a stock listing, and nothing here says that GTR Supply holds a particular item. Send the part number and the quantity you need and we will tell you where we stand.
What it is worth
What decides the number.
Condition is only part of it. These are the things that genuinely move a valuation in this line, and most of them are still in your hands when you write the list.
- Whether the drive uses conventional or shingled recording, which the four character prefix tells you and which decides who can use it at all
- Whether the drive is helium filled or air filled, since the two constructions sit at different capacity points and are wanted by different buyers
- Which line the DC name puts it in, because DC SN and DC SS parts are solid state and belong on separate lines from any spinning disk
- Whether a mixed pallet has been split by the sticker brand, which makes one family of parts look like three and does not work in a seller favour
- Generation within the DC HC series, because the capacity step between the 500 and 600 series is where the market for these drives changes
- The letter group in the middle of the part number, which carries the interface and the sector format and appears nowhere else on the label
- Self encryption and secure erase variants, encoded in that same letter group, which narrow who is able to deploy the drive
- Whether SanDisk heritage flash has been listed as flash rather than counted in with the hard drives on the same line
- Whether array pulls still have the array vendor carriers on them, which travel with the drive and are worth leaving fitted
Both sides of the desk
We supply it, and we buy it.
If you are buying
On the selling side GTR Supply supplies Ultrastar and HGST labelled drives in volume across the DC HC, DC HA, DC SS and DC SN lines, tested and graded, with the exact part number stated against every line on the manifest. Two things are worth saying with a Western Digital requirement specifically. Say whether shingled recording is acceptable for the workload, because a shingled drive at the right capacity is an excellent buy for archival and sequential work and a poor one for a random write array, and the four character prefix is the only thing that separates them. Then say whether you want spinning disk or flash, since DC SN and DC SS parts sit inside the same naming scheme and are not hard drives at all. Nothing on this page is a stock list, so send a part number with a quantity against it.
If you are clearing
On the buying side GTR Supply buys used Ultrastar drives in bulk, and the single most useful thing you can do before writing is not to split the pallet by the brand printed on the sticker. HGST, SanDisk and Western Digital numbers frequently describe the same family of parts, and three lines where there should be one makes a lot look more mixed than it actually is. List by part number instead, keeping the four character prefix intact, or photograph one label per stack and give rough counts. Put anything carrying a DC SN or DC SS name on its own line, because those are solid state and are valued on a completely different basis. Untested pallets are normal here and no test data is needed. Every drive is securely wiped and a certificate of destruction is available on request.
Common questions
WD Ultrastar, answered.
Is an HGST drive the same as a Western Digital drive?
For the enterprise lines, effectively yes. Western Digital acquired HGST in 2012, and the product lines were renumbered gradually rather than replaced, so HGST heritage part numbers stayed in production for years and are still on drives in circulation today.
An HUH number is an HGST heritage helium filled enterprise drive and an HUS number is the air filled line. WUH and WUS are the Western Digital numbers that succeeded them and describe the same kinds of drive. Western Digital also acquired SanDisk in 2016, which is why SDLF and similar prefixes appear on enterprise flash from the same house.
None of this indicates old stock, grey market goods or anything irregular. It is a naming history.
The practical advice for a seller is not to split a pallet into three lines because the stickers say three companies. List by part number and let GTR Supply group what belongs together, because a lot that looks more mixed than it is does not work in your favour.
How do I tell if an Ultrastar drive is SMR?
Read the four character prefix at the start of the part number. HUH, HUS, WUH and WUS drives use conventional recording, where the tracks do not overlap. HSH and WSH drives use shingled magnetic recording, where they do.
The difference matters because of how the two behave rather than how they perform on a specification sheet. Shingled drives reach higher capacities in the same physical space and are very good at sequential and archival work. Under sustained random writing they slow down markedly while the drive reorganises overlapping tracks, and in a general purpose array that behaviour can look like a failing drive when nothing is wrong at all.
So a shingled drive is not a lesser drive, it is a different tool, and the buyers for it are different buyers.
When you write a list for GTR Supply, copy the prefix exactly rather than describing the drive by capacity. Four characters settle the question, and no other field on the label does.
What does DC HC or DC SN mean on an Ultrastar drive?
They are the modern Ultrastar family names, and the two letters after DC tell you what kind of device you are holding.
DC HC is the high capacity helium filled 3.5 inch nearline line, and it is the bulk of what comes out of a storage refresh. The number after it rises with the generation. DC HA is the air filled 3.5 inch line at lower capacities, built differently for a different capacity band.
DC SN and DC SS are not hard drives at all. DC SN is the NVMe solid state line and DC SS is the SAS solid state line, and both are priced on a completely different basis from spinning disk. If your list has DC SN parts on it, they belong on separate lines from the hard drives.
One more label is worth recognising. WD Gold is the retail channel version of the enterprise platform, so a WD Gold number and an Ultrastar number can describe closely related drives. Send both if the label carries both.
Guides
Identifying it is half the job. These cover what a buyer actually does with your list once you send it, and what the words on a quote mean before you agree to any of them.
What to Check Buying Used Server Drives
How much life is spent, has it begun failing, and can you verify it. In that order, before price.
Drive Interfaces: SAS, SATA, NVMe and U.2
Start at the backplane, not at the drive. What your controller accepts is the question that costs money.
Grade A vs Grade B Hardware Explained
What a condition grade covers, what it cannot cover, and why the same letter means two different things at two suppliers.
Hardware we hold
Clearing it rather than buying
Trademarks
All product and company names are the trademarks of their respective owners. GTR Supply is an independent trader with no affiliation to, authorization from, or endorsement by any manufacturer named on this page.
Tell us the part number and the quantity.
Buying or selling. Send what you are looking for, or a photograph of what you are holding, and we will tell you where we stand. Pricing and valuations normally come back the same business day.
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