Ultrastar HS3xx or Exos 7E8 for specific data architecture

[jeyare]

new project for my friend

RS1221+ equipped with 2 pools:
3x6TB in RAID5 + 1x spare (HDD)
3x4TB in RAID5 + 1x spare (HDD)

4kn (native) 4096 Bytes per logical/physical sector is necessary for better performance (purpose definition)

Seagate 7E8 (6TB) ST6000NM022A & (4TB) ST4000NM001A are ok with this specs

However, no Ultrastar HC 5xx in such category is able to get the size 6TB or 4TB and 4kn sectors, except HC3xx - but it is necessary to replace sector def. by some WD tool "Hugo", which isn't public.
What I found, there is also a 3rd party utility to change sector values for WD/Ultrastar drives (same ATA commands must be there like in the WD):

GitHub - pig1800/WD4kConverter

Contribute to pig1800/WD4kConverter development by creating an account on GitHub.

github.com

just to be sure - don't use this utility for a "live" disk

then HUS726T6TALE6L4 (6TB) and HUS726T4TALE6L4 (4TB) are applicable

From a general preview, both 7E8 and HC3xx have the same specification. Except one - helium-filled in the case of HC3xx.
Follow Seagate detailed (as usual) Product Manual - both HDDs contain 3 or 4 platters (4 / 6TB capacity version).
No such mention about the HC3xx from WD. As I found in the external 3rd party HDD DB - HC3xx contains also 3 or 4 platters, by capacity (1.33 and 1.5 TB per platter).
Conclusion:
- HDD equipped with 3 or 4 platters doesn't need helium as a gamechanger.
- The cost difference is about few EUR/pcs.

Then it is absolutely up to you, with one important factor - don't forget to rewrite the logical sector in HC3xx. Otherwise, you will get a slower HDD.

PS:
here is another example of "not good idea to mix HDDs within RAID". Don't mix diff. sector formats. Never.