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Comment by PixelOfDeath | Hacker News Reader

With the introduction of QLC consumer SSDs, with worse write endurance and life time but the same price as TLC, I took a look at used enterprise SSDs and never looked back.

The only issues is the connectors. You need 8x PCI-E lanes (4x might work) or a SAS connector that nearly no consumer board has.

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Or you could... not buy QLC.

Do you have any recommendations? How does the price per TB compare?

I got myself a used pm1725b (PCI-E v3 8x) with 3.2TB for 400€.

It hat ~350TB written, and according to Samsung is rated for 3 full device writes per day for 5 years = 17280 TB. So I have some wriggle room left.

They use lots of capacitors to hold written data in a dram and flush it out to flash on sudden power down. So they can optimize write operations for speed and low flash wear. Write speed and endurance is the part where consumer SSDs suck more and more ass.

Annoyingly many sellers do not put up the written amount of data. But I think that is more out of ignorance and less to try to dump worn down devices.

U.2 to PCIe mounter or U.2 to M.2 cable is fine.

I would not trust a cheap chinese PCI-E to U.2 connector. And used SAS cards become kind of hot and need active cooling. So why not just directly go for a PCI-E SSD?

QLC is complete trash and should never be used outside of a WORM architecture in a larger pool. That they are trying to force it on consumers is criminal. Same with SMR.

>QLC is complete trash and should never be used outside of a WORM architecture in a larger pool.

Not everyone is a creator editing/rendering 4k videos. For the typical surfer/office worker/gamer QLC drives are fine because they rarely need to dump 50+GB of writes at a time. What you're suggesting is basically "ban all atom processors because they're criminally slow!"

I think they were complaining about reliability. QLC cells can't handle as many writes before failing.

QLC also has shitty slow write speed. (Slower then linear writes on spinning rust!)

So consumer SSDs now depend on a limited dynamic part of flash being used as SLC to cache writes. Just that this dynamic part mostly gets smaller the fuller the device is.

And as soon as you do anything with large writes you will hit a brick wall of slowness, on full devices sooner then on empty ones.

The minimum size of the cache doesn't have to be bad.

And I bet the vast majority of people basically never do >10GB writes at >200MB/s.

Yes many consumers will be fine with this drivers.

But the information about the limited write cache never gets mentioned by the manufacturers. So people that actually need to write large amounts of data from time to time, fall into a performance trap.

QLC drives, reasonably designed, can meet most consumer endurance needs.

Samsung 980 is rated for 0.3 DWPD. For a 250 GB drive that's 75GB per day. I have a hard time imaging what type of workloads would cause the target audience (ie. surfers/office workers/gamers) would reach that limit on a consistent basis.

It's worse than that. Most people do use their drives so it runs out of SLC cache and most QLC drives are low end and don't come with DRAM. The systems they're put in are usually equally low end with low system RAM so the OS is going to page a lot. QLC has atrocious write endurance so these devices are going to eventually run out and either die or go RO. QLC devices in consumer electronics are essentially just ewaste and waste wafers. SLC->PLC is a case of diminishing returns in terms of storage/area. I do actually think we need to attach warning labels for QLC drives/devices. Same for SMR HDD's.

Current consumer QLC devices still do very well in read speed and especially latency. The latency often is better then on older enterprise SSDs.

Only device managed SMR is terrible. Host managed SMR is fine for data-hording if the savings in size/price are forwarded.

>Host managed SMR is fine for data-hording if the savings in size/price are forwarded.

Exactly. When you architect your tiered data storage solution to take advantage of technologies such as SMR/QLC it works great. This is absolutely not the case in consumer applications. Consumers will use QLC for their boot drives and fill their NAS boxes with SMR drives and have a horrible experience.

> Host managed SMR is fine for data-hording if the savings in size/price are forwarded.

I'll believe it when I see it, though.

Unless you're trying to cram more data into a 2.5 inch drive, there seems to be zero upside to getting an SMR drive. They're priced about the same per byte despite "25% density improvements", and the high capacity 3.5 inch models on the market don't use it.

> and the high capacity 3.5 inch models on the market don't use it.

Sure they do. WD sold device managed SMR 3.5 disks without telling anyone. And then people noticed because of absolutely terrible raid re-silvering performance.

The consumer market is absolute trash for SMR devices, all the disadvantages with no benefit. But you can be sure that the enterprise sector gets host managed SMR drives at a better size/price ratio.

What's your definition of "high capacity"?

The biggest SMR drives I can buy are 6TB or 8TB.

The biggest non-SMR drive I can buy is 18TB.

Harder to find because they obviously do not market this things towards consumers. Except when selling consumers SMR drives without telling them. ;)

https://documents.westerndigital.com/content/dam/doc-library...

Wow, both sold out and $40/TB.

And yeah that's why I said on the market rather than 'in existence'.

Enterprise prices are always negotiated in secret. We don't get to see what e.g. Facebook or Google pay for this devices.

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