this post was submitted on 08 Mar 2025
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So can someone make 3.5" SSDs then????
They can be made any size. Most SATA SSD are just a plastic housing around a board with some chips on it. The right question is when will we have a storage technology with the durability and reliability of spinning magnetized hard drive platters. The nand flash chips used in most SSD and m.2 are much more reliable than they were initially. But for long-term retention Etc. Are still off quite a good bit from traditional hard drives. Hard drives can sit for about 10 years generally before bit rot becomes a major concern. Nand flash is only a year or two iirc.
Longer if it has some kind of small power. I think I read that somewhere.
Why? We can cram 61TB into a slightly overgrown 2.5” and like half a PB per rack unit.
Because we don't have to pack it in too much. It'd be higher capacities for cheaper for consumers
Also cooling
It’s not the packaging that costs money or limits us, it’s the chips themselves. If we crammed a 3.5” form factor full of flash storage, it would be far outside the budgets of mortals.
You could make the chips bigger, which should be cheaper to produce.
Nope. Larger chips, lower yields in the fab, more expensive. This is why we have chiplets in our CPUs nowadays. Production cost of chips is superlinear to size.
Then lower the storage density. Making things as small as possible almost always ends up being more expensive.
Lower storage density chips would still be tiny, geometry wise.
A wafer of chips will have defects, the larger the chip, the bigger portion of the wafer spoiled per defect. Big chips are way more expensive than small chips.
No matter what the capacity of the chips, they are still going to be tiny and placed onto circuit boards. The circuit boards can be bigger, but area density is what matters rather than volumetric density. 3.5" is somewhat useful for platters due to width and depth, but particularly height for multiple platters, which isn't interesting for a single SSD assembly. 3.5 inch would most likely waste all that height. Yes you could stack multiple boards in an assembly, but it would be better to have those boards as separately packaged assemblies anyway (better performance and thermals with no cost increase).
So one can point out that a 3.5 inch foot print is decently big board, and maybe get that height efficient by specifying a new 3.5 inch form factor that's like 6mm thick. Well, you are mostly there with e3.l form factor, but no one even wants those (designed around 2U form factor expectations). E1.l basically ties that 3.5 inch in board geometry, but no one seems to want those either. E1.s seems to just be what everyone will be getting.
Not economical. Storage is already done on far larger fab nodes than CPUs and other components. This is a case where higher density actually can be cheaper. ”Mature” nodes are most likely cheaper than the ”ancient” process nodes simply due to age and efficiency. (See also the disaster in the auto industry during covid. Car makers stopped ordering parts made on ancient process nodes, so the nodes were shut down permanently due to cost. After covid, fun times for automakers that had to modernise.)
Go compare prices, new NVMe M.2 will most likely be cheaper than SATA 2.5” per TB. The extra plastic shell, extra shipping volume and SATA-controller is that difference. 3.5” would make it even worse. In the datacenter, we are moving towards ”rulers” with 61TB available now, probably 120TB soon. Now, these are expensive, but the cost per TB is actually not that horrible when compared to consumer drives.
Skill issue
Given that there are already 32TB 2.5” SSDs, what does a 3.5” buy you that you couldn’t get with an adapter?
Native slotting into server drive cages. No concerns about alignment with the front or back.
The market for customers that want to buy new disks but do not want to buy new storage/servers with EDSFF is not a particularly attractive market to target.
What kind of server? Dell's caddies have adapters, and I'm pretty sure some have screw holes on the bottom so you don't need an adapter.
They should be cheaper since theres a bunch more space to work with. You don't have to make the storage chips as small.
Chips that can't fit on a 76mm board do not exist in any market. There's been some fringe chasing of waferscale for compute, but it's a nightmare of cost and yield with zero applicable benefits for storage. You can fit more chips on a bigger board with fewer controllers, but a 3.5" form factor wouldn't have any more usable board surface area than an E1.L design, and not much more than an E3.L. There's enough height in the thickest 3.5" to combine 3 boards, but that middle board at least would be absolutely starved for airflow, unless you changed specifications around expected airflow for 3.5" devices and made it ventilated.
A big heat sink like they used to put on WD Raptor drives.
A better price as low density chips are cheaper.
And you can fit in more of those in a bigger space = Cheaper.
The lowest density chips are still going to be way smaller than even a E1.S board. The only thing you might be able to be cheaper as you'd maybe need fewer SSD controllers, but a 3.5" would have to be, at best, a stack of SSD boards, probably 3, plugged into some interposer board. Allowing for the interposer, maybe you could come up with maybe 120 square centimeter boards, and E1.L drives are about 120 square centimeters anyway. So if you are obsessed with most NAND chips per unit volume, then E1.L form factor is alreay going to be in theory as capable as a hypothetical 3.5" SSD. If you don't like the overly long E1.L, then in theory E3.L would be more reasonably short with 85% of the board surface area. Of course, all that said I've almost never seen anyone go for anything except E1.S, which is more like M.2 sized.
So 3.5" would be more expensive, slower (unless you did a new design), and thermally challenged.
Build quality
Relevant video about the problems with high capacity ssds.
https://www.youtube.com/watch?v=Y2i8wZCXDF4
I'm not particularly interested to watch a 40 minute video, so I skinned the transcript a bit.
As my other comments show, I know there are reasons why 3.5 inch doesn't make sense in SSD context, but I didn't see anything in a skim of the transcript that seems relevant to that question. They are mostly talking about storage density rather than why not package bigger (and that industry is packaging bigger, but not anything resembling 3.5", because it doesn't make sense).
Fourty minutes? Yeah, no. How about an equivalent text that can be parsed in five?
I want them like my 8" floppies!