Hdd-uri de capacitate mare - cela mai avantajoase (cost/fiabilitate)?

Totuși, riscul de a apărea problema poate fi și de 4-5 ori mai mare în anumite situații.

TL;DR
I've asked and been given hard drive manufacturing answers by someone within the industry.
I can't and won't ask or disclose anything that may lead to this person's identity, employer or position.
I have no agenda in sharing the following other than keeping with my general goal here of helping and learning from others, as shown by the majority of my posts.
Begin Q&A
I've been very fortunate to have been contacted by someone within the hard drive manufacturing industry because of some of my posts. I can't disclose whom this person is, but from my layman's understanding of additional undisclosable detailed information, I'm fully confident this person is whom/what they claim to be.
I was able to ask some questions and was given some very interesting info that confirms what I've posted and others have speculated about.
I hope we'll be able to ask more questions in the future, but understand that both I and my source may refuse to ask or answer any question publicly for confidentiality reasons.
Q: A CMR drive be changed to DM-SMR or only HM or HA-SMR? There's a conspiracy theory that the manufacturers may try to submarine SMR into their drives in the future. IMO, it would be market suicide!
A: In general, SMR drives use the same hardware (heads and platters) as CMR drives. SMR just has the tracks closer so you get more capacity. DM-SMR is the consumer level version that was created to reduce manufacturing cost on lowest capacity drives. It was predicted that SSD was going to take over low capacity HDD’s years ago. The goal of DM-SMR is to reduce manufacturing costs while maintaining acceptable performance in intended applications (light duty consumer applications).
On the opposite end of the market, for Cloud, they want as much capacity as possible, so that’s why we use SMR there as well. They demand consistent performance though, for their customers in turn. So HM-SMR is sold to that market. You get the benefit of the closer tracks (so more physical tracks on the same platter) at the cost of writing a whole 256 MiB zone at once, because every 256 MiB there’s a “gap” in the SMR tracks. HM-SMR requires a file system and storage driver that are aware of the HM-SMR rules. If there’s data already in one of those SMR zones, you can’t just write in the middle of one of those zones, without resetting that zone first. Otherwise it would be way too easy to overwrite data in that zone. The HDD firmware keeps track of where we are allowed to write within zones and on HM-SMR drives, you can ask the drive for those values, called “write pointers”. HA-SMR isn’t popular anymore and I don’t know if anyone is still making those. Hybrid SMR is also out there in the world, where you can convert any individual 256 MiB zones between SMR and CMR. Those require special kernel and HBA/controller firmware and OS and file systems to work.
Also, for HM-SMR, there’s a beta version of BTRFS that mostly works. Might be worth mentioning. You can Google “btrfs hmsmr” for tutorials. I probably wouldn’t use it for production data but if you end up with one of those HM-SMR drives, it works well enough for Chia or something.
My notes: I posted about HM-SMR in this thread: https://www.reddit.c...mr_and_dropbox/
Q: Is it true that the drives in externals can be: overstock, overruns, binned (out of spec drives), from cancelled orders.
A: Yes to all of it. Externals are the lowest bins above the [redated] (Edit: binned rives} we sell to third parties. It’s whatever is leftover. They have less warranty because they aren’t expected to last as long.
My notes: The first part is supported by what I posted in this thread, https://www.reddit.c...s_inside_my_wd/ which has a link to WD's disclosure about this.
It's been confirmed by another source that the binned drives, are drives that are Out Of Spec, flashed with special firmware that can't be updated and is no longer supported by the manufacturer. This is source of SOME of the unbranded drives from certain resellers.
Q: Is it true that in a given generation of HDD, when reduced capacities are released at the same time, you can sometimes tell from the model number that it’s the same hardware inside as a full capacity drive” To be used in externals or sold to resellers?
A: Yes, see above. The [redated] (My edit: XX drive size) were reconfigured for 12 and 14TB. The [redacted] went all the way down to 10TB to my knowledge. We just disable specific bad heads in the factory and rewrite the tracks. It’s an automated process obviously, but we can internally look up all that history on any serial number.
Q: Is it true that some or all drives of a particular size come from the same hardware line and only the firmware determines which line, e.g. Home, Survelliance, NAS, Datacenter, Enterprise it's labeled as. Or are there separate lines for each type?
A: Yes, kind of. In the spirit of the question, yes, especially in recent years. The firmware is different for those markets, and specific hardware might be binned for those markets too. For example, surveillance firmware is tuned to be performing writes for the vast majority of the time and to handle data streaming better, as in from cameras. Some of the caching and performance features are disabled, and the reliability features are tweaked to be less likely to interrupt that incoming data stream.
My note: To my layman's understanding, this doesn't mean that ALL drives of a given size are the same. Just that SOME drives of a given size MAY be from the same line.
Also note that "binned" as used in the answer doesn't necessarily mean lower or better performing or drive specs. Just different for different uses.
Q: Is it true that drives that don't meet the full specs can be binned and their firmware permanently changed to a lower spec drive, then sold to resellers?
A: Yes. The firmware doesn’t change the drive to a lower quality drive, it is the manufacturing imperfections. Head fly height is less than 5 nanometers, but if any of those heads touch the disk, the head suffers damage. And there are a lot of heads in high capacity hard drives now. Temperature and humidity affect the aerodynamics of the heads at that level so that is adjusted constantly within the firmware. Usually it’s 20 heads per drive, and even if we bin the parts before assembly, sometimes we figure out in the factory that one or more heads can’t meet the reliability requirements, so we permanently disable them in the firmware.

Eu am doar seagate, 3 de 18tb, 1 de 16tb, 1 de 12tb, 1 de 8tb (SMR), 5 de 4tb, cateva de 3tb si 2tb. Doar unul de 8TB a murit si era SMR.
Cu siguranta o sa anunt cand mai pica vreunul.