How to Read WD and Toshiba Model Numbers

Western Digital: capacity then suffix

A WD drive number is WD, then the capacity, then a suffix of four letters. WD40EZAX is WD, 40 for 4TB, then EZAX. Capacities below 10TB use two digits for terabytes; at 10TB and above the pattern shifts to three digits, so WD101EFBX is 10TB and WD181KFGX is 18TB.

The suffix is where the product line lives, and unlike Seagate's generation digits it is reasonably readable once you know the families.

The middle letters generally identify the line and the last letter tends to move with generation. That is a useful heuristic rather than a rule, and it breaks often enough that you should verify rather than assume.

The WD suffix that matters most

EFAX is the suffix worth recognising on sight. Those are the WD Red models at 2TB, 3TB, 4TB and 6TB that shipped with shingled recording into a NAS-marketed line without it being stated, which produced the 2020 controversy and the litigation that followed.

WD's response was to publish a model-level list of which client drives are shingled, and to split the Red line: Red Plus with the EFZX, EFPX and EFRX suffixes is the conventionally-recorded NAS line, and Red Pro above it. If you are buying a WD NAS drive today, Plus or Pro is what you want and plain Red is a name to be careful with.

The other pair to know is within WD Blue at the same capacity. WD20EZBX is conventional and WD20EZAZ is shingled, one letter apart, same family, same 2TB, opposite answers. That is the WD equivalent of Seagate's 1TB BarraCuda problem.

Toshiba: the mechanism prefix does most of the work

Toshiba numbers its bare mechanisms and its retail cartons differently, and the mechanism number is the informative one.

DT01ACA is the conventionally-recorded 7200rpm desktop mechanism, covering 1TB, 2TB and 3TB. DT02ABA is the shingled 5400rpm mechanism, covering 2TB, 4TB and 6TB. That split is close to a clean rule: DT01 is conventional, DT02 is shingled, and Toshiba's own product overview for the DT02 series states drive-managed shingled recording explicitly.

The retail P300 cartons map onto those mechanisms. HDWD110, HDWD120 and HDWD130 are the 1TB, 2TB and 3TB conventional drives. HDWD240 and HDWD260 are the 4TB and 6TB shingled ones, and Toshiba names both in its April 2020 SMR statement.

So a P300 can be conventional at 7200rpm or shingled at 5400rpm depending only on the capacity you picked, under one product name. It is the same trap as the others, expressed differently.

What none of these codes will tell you

The WD suffixes and the Toshiba prefixes are more informative than Seagate's generation digits, and they are still not a substitute for looking the model up.

WD changes suffix letters across generations, so a pattern that holds today may not hold for a drive released next year. Toshiba's DT01 and DT02 split is clean now and is a mechanism naming convention rather than a promise about future products.

The reliable move is the same for all three manufacturers: read the part number off the label, look it up against the maker's own document, and treat anything unverified as unverified rather than as probably fine.

Our resolver does that lookup and names the document. If a model is missing, search it anyway, misses decide what gets verified next.

Decoded models with a sourced recording answer

65 part numbers from the makers this guide covers where a manufacturer document states the recording technology. Each page names the document. Models not listed here are not shown to be shingled - their technology is simply not sourced yet.