I was really hyped about U.2 connector on my motherboard, assuming I’ll get some nice Optane drive as dedicated SWAP device but then it turned out… Optane is dead. And that rises two questions:
You can still buy Optane! 900p/905p 2.5" U.2 drives are fairly affordable.
U.2 drives still exist, through other mfrs. [WD, Intel non-Optane, Toshiba/Kioxia, HGST…]
U.2 contains four PCI-E express lanes just like M.2, but U.2 is also pluggable. Since it’s so similar you can get passive adapters for U.2 <-> M.2.
U.2 drives are quite common in the enterprise.
Get an Icy Dock hot swap.
I have a P5800X 1.6TB in one of my U.2 ports and it seems to get better scores than what I’ve seen others post online. I only updated my computer recently, so the performance gain is probably due to a combination of more recent AMD drivers as well as using a high quality u.2 cable.
Other than Optane, you can get very large U.2 NVME drives if you’re willing to sell a kidney or two
You can get the large Micron 9300’s for ~$100/TB used on eBay
That would be only half a kidney 
Please note that these are enterprise drives that get really hot and demand enterprise class air flows for cooling.
And if you’re patient, you can get them even cheaper. Picked up a few 7.68TB Intel D7-P5510’s for $580 each a while back.
Hmm… The top review for that ebay listing sure is peculiar. Is there such a thing as coil-whine for SSDs? LOL
I replaced a noisy SSD raid array with this drive over thunderbolt and it is quiet and fast.
Does that even work under windows? None of my U.2 Optane drives seem to be hotswappable despite a lot of fiddling with the BIOS settings.
I have an Icydock NVME PCIe enclosure and it doesn’t support hotswap. But that was never really part of the NVME spec to start with. U.2 on the other hand is supposed to have this feature so I’m thinking it’s probably more of a Windows issue.
Does Optane still provide better latency / iops than gen4 ssds? If so then I guess getting second hand 905/900p really would make sense
That’s an interesting question.
SSDs behave quite differently depending on the workload.
Optanes are exceptional at latency and still blow every NAND drive away - even the latest ones.
That’s great only for a handful of applications. E.g. databases with lots of random access.
However, the Samsung 980 Pro 1TB is capable of achieving > 1M IOPs with sufficient concurrent access, while the older Optane 900/905 only achieve 250k IOPs.
There is lots of work required to really get these benefits out of these SSDs, though.
Desktop and home office applications rarely see concurrent access at the level that would bring out these top performances.
I’m honestly considering it purely for SWAP drive for TR5965WX build because 1TB of RAM is still quite pricey lol. I already got 256GB RAM and I’d like to add 1TB dedicated SWAP device to that. Optane used to be no brainer for this task however Gen4 NVME SSDs made it significantly less obvious choice… So now I’m again not sure. I guess I’ll get that optane though. It seems to be interesting, one of a kind device that is just worth trying out at least until they’re still relatively easily available.
I forgot whom to attribute the quote to: “memory is like sex - it’s better if you don’t have to fake it”.
I have not configured swap on my computers for years …
Well I still think Optane was really interesting twist in the field of memory. Especially DIMM form factor one. I find it really neat to be able to get lots of memory slower than system RAM. Especially since you can’t really mix and match RAM sticks so you can’t get like 4 small fast 3200 or even more RDIMMs and 4 crappy big 1600 LRDIMM sticks (not that they’re actually much cheaper in the first place which even amplifies my point). Gap between NVME and RAM performance (and price) is still quite big especially in terms of latency. Optane closed that gap quite significantly and added another memory tier. Too bad it’s dead 
Doorstop! I vote Doorstop!
I used quite a few things as doorstops over the years. Including some no-longer useful PC parts ;D I think i even used an old motherboard as a doorstop for a while, and I probably shouldn’t mention using an old video card as a coaster … ah heck with it. Why not? 
Use Optane, it never dies.
Okay, I may be a bit dense on this subject, but what is the advantage of a U.2 drive versus an M.2 drive? I’ve never used a U.2 drive, so I’m not sure what the advantages are. I have used several M.2 drives before, and have them in my computers now (I have 3).
In a server a U.2 drive can be hotswapped. M.2 drives cannot, you have to shut down your computer to swap them. U.2 drives also have a similar 2.5" footprint as Sata/SAS SSDs, so you can pile a lot more flash in them - for example you can get 16TB U.2 SSDs.
As a consumer you don’t have to worry about U.2.
Basically they have considerably more room for
Generally these sorts of drives are enterprise drives. This means they:
The new and fickle nature of PCIe 4.0 connector cables means actually attaching drives can quickly get very expensive if you don’t already have a server box meant for them.
There are also SATA U.2 drives, which are comparably hard limited on throughput and significantly worse latency, but are intended for maximum possible storage capacity. You aren’t going to be buying a +30TB drive for a long time though.
Basically you don’t need their kind of performance, and if you did, the used enterprise 22110 M.2 sticks will probably suit you fine for less overall cost.