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Hard drive capacity limitation - a legend?

January 3rd, 2020, 20:30

Hi, everyone,
As in the topic:
Product datasheet of HitachiGST hard disk models - HDS7230xxALA640 - explanation:
HDS723030ALA640 = 3TB, 64MB buffer
H = Hitachi
D = Deskstar
S = Series prefix
72 = 7200 RPM
30 = Full capacity — 3TB
30 = Capacity this model, 30 = 3TB
(20 = 2TB, 15 = 1.5TB)
A = Generation code
L = 26.1mm z-height
A6 = Interface, SATA 6Gb / s
4 = 64MB buffer
0 = Reserved (2 = Reserved)

What does it mean in the explanation that:
*** "30 = full capacity = 3TB"
*** "20 = capacity [this model] = 2TB"

It would not be easier to write simply: "capacity of this disk model = 2TB"?
Can it be related to the fact that the whole family of disks with max. capacity 3TB (as in the example above - the HDS7230xxALA640 model family) is divided into 3 parts:
a / model with full capacity 3TB - 3030. capacity limitation not installed.
b / model 3020 with capacity limited to 2TB. The same model without this limitation would have 3TB.
c / model 3015 with capacity limited to 1.5TB. The same model without this limitation would have 3TB.
Of course, according to serious specialists - "these are unauthorized rumors and sick speculations of sick people". Maybe yes?...
But the question of total, absolute, 100% non-specialist remains:

*** Does the 3030 model have a different number of plates than the 3020 in the HDS7230xxALA640 family? or 3015? Or maybe the same, only smaller?
*** Or maybe in these 2TB and 1.5TB models - some plates are not covered with magnetic media? Or something else is the reason for these capacity differences.
What is this?
*** For what technical reason the 3020 (2TB) and 3015 (1.5TB) models have less capacity than 3030 (3TB)?
All information is greatly appreciated. Thank you for them on behalf of myself and (I hope) many users not only Hitachi / HitachiGST / HGST drives but any hard drives.

Re: Hard drive capacity limitation - a legend?

January 3rd, 2020, 23:36

Start by reading the manuals.

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/data-center-drives/ultrastar-sata-series/product-manual-ultrastar-7k3000-and-3tb-deskstar-7k3000-sata.pdf

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/hgst/deskstar-7k-series/product-manual-deskstar-7k3000-2tb-capacity-and-below.pdf
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