Why do U2 drives use so much power compared to M2?

[UnknownPommes]

So have been looking for drives for an upcoming (somewhat power consumption oriented) project and
literally all u2 drives are between 15w and 25w each, i am planing to use 4-6 drives for redundancy that would be over 100w in ssds at load!
M2 on the other hand with comparable specs (tbw, nand type, iops and seq) use like not even 1w according to specs,
why is there this extreme difference in power draw for similar specs?
is this just because the longer cable / connection?
for the u2 drives what usage can be expected at idle / low load - os idle?

Thinking of using a x16 to 4x m2 slot riser board and just going m2 bc from what i have seen the only real benefit of u2 would be hotswap when used with sff front bays, given there are m2 ssds with decent performance and several pb of tbw (like the mte220)

Also what do you think of those u2 to m2 adapters, would they have a huge impact on power draw or just combine the best of the two types?
(https://www.amazon.de/StarTech-com-M-2-auf-U-2-Adapter/dp/B073W65QX6)

Thanks for any input


Edit:
Should have mentioned, looking for around 2-3tb and 300k-500k iops / drive


Sources / List with power draw: List of Intel SSDs - Wikipedia

 

[Tech Junky]

I think it's all relative to how the drives can be used.

M2 usually means it's in a confined space and heat has to be mitigated by lower power due to the inability to use active cooling.

U2/3 though have a 2.5" chassis for passive cooling and aren't used in confined spaces like a laptop since they don't have the connector to do so.

I recently switched from spinners to M2 > U3 setup.
https://www.amazon.com/dp/B09HTPWLXM - M2 adapter
https://www.amazon.com/dp/B09BFL485F - drive cable

I started out with a Micron drive and somehow managed to kill 2 of them but, I think the issue was more of the existing setup more so than the drives themselves. I started off using PCB mounts into the slot directly to mitigate any potential for attenuation through a cable which indeed did happen when switching to the M2 cable pairing. The initial cable I ordered was 100CM and didn't work but switching to the 50CM cable did work just fine.

As to the power consumption I don't think it's a huge deal when comparing them to spinners which is the alternative when looking for flash capacity vs M2. The trade offs are M2's 8TB will run you $800 where you can get U2/3 options for ~$400. M2's have a max capacity of 8TB where U drives can hit 16/30/60+ TB in size.

Supported Power States
St Op     Max   Active     Idle   RL RT WL WT  Ent_Lat  Ex_Lat
 0 +    25.00W   25.00W       -    0  0  0  0   500000  500000
 1 +    12.00W   12.00W       -    1  1  1  1   500000  500000

A lot of research might be needed with these though as they vary wildly from one brand/model to another in terms of speed / power / etc. I wanted something on par with my OS drive in terms of speed as to not bottleneck the performance when doing anything so, I went a bit higher end in terms of drives.

Also what do you think of those u2 to m2 adapters, would they have a huge impact on power draw or just combine the best of the two types?
(https://www.amazon.de/StarTech-com-M-2-auf-U-2-Adapter/dp/B073W65QX6)

Why? That just complicates things.
https://www.amazon.com/gp/product/B0C3HGSBGD

This allows you to mount a U2/3 directly to the card and stick it in the slot. One thing to remember though is your adapter can be U2 and work in either but, if it's U3 it will only work with U3 drives.

 

[nexox]

the only real benefit of u2 would be hotswap

U.2 hot swap is more complicated than just mounting them in removable trays, since they're PCIe devices there are various things the bios and OS have to do to make this actually work without a reboot, from my brief research this isn't common on the sorts of systems home labbers tend to run - even my dual sky lake board can't manage it.

The real advantages to U.2 are guaranteed PLP, lower price/TB, higher capacity, and the typical benefits that come with enterprise SSDs, like write endurance.

 

[Jorge Perez]

You can get 4TB M.2s for the $130 range, which is the lowest cost/GB there is.

 

[nexox]

You can get 4TB M.2s for the $130 range, which is the lowest cost/GB there is.

Ah, right, I tend to ignore that grade of SSD and forgot what the prices were. I'd argue that with the reliability complaints people have had with the cheapest m.2 drives they could still cost more in the long run.

 

[Tech Junky]

You can get 4TB M.2s for the $130 range, which is the lowest cost/GB there is.

You can but, do you want to? There are some cons to going dirt cheap on storage. The specs for that drive are going to be considerably lower than another model.

Speed / warranty / durability

 

[CyklonDX]

as additional thing; Most u.2 disks also include powerloss protection, and charge with enough time to flush data to nand.
A comparable nvme with powerloss protection also takes from 8-16W under load.

 

[mattventura]

U.2 and friends tend to throttle less under load since the casing can sink a lot more heat.

If you want to know if hot swap will work for you, the only way to really find out is to try. Some boards might support full-on surprise hotplug, others might support coordinated hotplug (manual disable before unplugging, pci rescan when plugging in). You can sometimes also get support on a board that wouldn't support it natively by using a switch card. A good indicator for this is Thunderbolt support - if the board supports TB, or supports a TB addon card, then there's a very good chance that the BIOS understands hotplugging at least from a PCIe topology standpoint (the slot itself may also need a hotplug controller, but the aforementioned switch card can handle that).

 

[Whaaat]

M2 on the other hand with comparable specs (tbw, nand type, iops and seq) use like not even 1w according to specs,
why is there this extreme difference in power draw for similar specs?

The difference is not extreme. Don't look at different vendors and "comparable specs" models , look at the same nvme drive but in different form factors, you'll find info like this:

for the u2 drives what usage can be expected at idle / low load - os idle?

2W to 4W typical

 

[UnknownPommes]

The difference is not extreme. Don't look at different vendors and "comparable specs" models , look at the same nvme drive but in different form factors, you'll find info like this:
View attachment 32476

2W to 4W typical

what ssd is this from?

 

[Whaaat]

what ssd is this from?

Micron 7300

 

[mmk]

U.2 hot swap is more complicated than just mounting them in removable trays, since they're PCIe devices there are various things the bios and OS have to do to make this actually work without a reboot, from my brief research this isn't common on the sorts of systems home labbers tend to run - even my dual sky lake board can't manage it.

I'd like to disagree with you here. Dells from the NVME-enabled r730xd (so basically their first system with U.2) onwards support hotswap just fine at least in Linux. However HPE has some server models (dl380 gen9?) where hotswap support is broken on the hardware level and they basically said they're not fixing it. Newer systems work better.

You probably want to run as new OS as possible though because NVME support has definitely improved since something like RHEL7. Have encountered the odd kernel panic back in the day.