We decode 146 drive and memory part numbers from manufacturer documentation - 123 of them with live prices attached. Each page shows what the vendor documents each segment to mean, which sibling part numbers it is confused with and how they differ, and how to check whether a specific unit actually carries a warranty.
A part number search is one of the most specific things a buyer can type, and one of the worst served. Search a string like ST20000NM007D and you will get a page of individual store listings, each selling that exact drive and none explaining what it is, how it differs from the near-identical part number one digit away, or whether the unit being sold carries a warranty. There is no neutral answer anywhere on the first page. That is the gap these pages exist to fill.
The confusion starts because several organisations name the same physical drive. The manufacturer assigns a model number that genuinely describes the product - family, capacity, interface, sector format. A server vendor buying that drive in volume assigns its own spare-part number so it can be stocked and ordered through their service system; that number identifies a service part, not a specification. Distributors and integrators sometimes add a third. All three appear in listings, and none of them looks like the others.
The manufacturers differ sharply in how much of their own numbering they explain. We decode only the fields the vendor defines in its own documentation, and say so explicitly where a segment is not documented by anyone. That makes our tables shorter than the blog posts ranking for these terms, and correct where those are guessing.
The single most expensive thing a part-number buyer can get wrong is assuming that a drive with a manufacturer part number carries a manufacturer warranty. Very often it does not. OEM stock, pulls from integrator inventory and gray-market units all reach the market under the maker's own numbering, and some retailers state plainly on the listing that the manufacturer warranty is none. The seller may offer their own cover, which is a different promise from a different company with different terms.
Every part-number page here carries a warranty section that links the manufacturer's own checking tool. We link it rather than reproducing results, because the answer depends on the individual serial number in the drive you are holding, and only the manufacturer can answer it. Our warranty pages set out the seller-versus-manufacturer distinction in full.
Entries marked ref are reference pages: part numbers we document and decode but do not currently have a live listing for. They exist because the question “what is this part number” has an answer whether or not anyone is selling one today.
Because several different organisations name it. The manufacturer assigns a model number that encodes the family, capacity and interface. A server vendor who buys that drive in volume assigns its own spare-part number to the same physical unit, so it can be stocked and ordered through their service channel. A distributor may add another. All of them identify the same drive, which is why searching one number often returns results that look like a different product.
A manufacturer model number describes the product: an ST20000NM007D tells you the maker, the family, the capacity and the interface. An OEM spare number like 695842-001 identifies a service part in a vendor's own catalogue - it says which product it replaces, but its characters do not describe the hardware. The practical consequence is that a drive sold under a spare number frequently carries no manufacturer warranty, because it was never sold to you as a retail product.
Partly. Seagate, Western Digital and Toshiba publish documentation defining some of the fields in their model numbers - the family prefix, the capacity field, the interface characters. Those are the segments we decode on these pages, each with the vendor document that defines it. Other characters are not publicly documented by anyone, and we say so rather than repeating a community guess as though it were a specification.
Because we only decode what a manufacturer documents. There is a substantial body of community knowledge about what the trailing characters of a Seagate or WD part number mean, much of it probably correct, and none of it published by the vendor. Printing an unsourced reading inside a table headed "what this means" would make us the citation for something nobody can verify. Shorter and correct beats longer and confident.
No, and this is the trap that costs buyers the most. Warranty coverage depends on how the unit entered the market and whether it was ever registered, not on its part number. OEM and gray-market stock frequently carries no manufacturer warranty at all - some retailers state this plainly on the listing. Every part-number page here links the manufacturer's own warranty checker so you can enter the serial and get the answer from the source.
It is the sector format, and it is one of the few genuinely consequential differences hidden inside a part number. 512e drives emulate 512-byte sectors over 4K physical ones; 4Kn drives present 4K natively. A 4Kn drive will not simply drop into an array or controller expecting 512e. Where the vendor documents which variant a part number denotes, our decode table says so.