3 ms·

Not sure how are these nvme enclosures supposed to work. The problem is right in the picture. Samsung SSD bla bla 3.3V/3.3A = 11W and that's just for the SSD it

by megous 4y ago

Not sure how are these nvme enclosures supposed to work. The problem is right in the picture. Samsung SSD bla bla 3.3V/3.3A = 11W and that's just for the SSD itself, the controller chip in the enclosure will also consume a lot of power at the advertised speeds. So you're looking at say 13W or so peak power consumption of the whole deal. Normal USB 3.0 port can do 4.5W. So sticking that contraption into such port will not work reliably at all. Specially marked USB 3.0 port can deliver maybe 7.5W. Type-C ports, who knows. Depends on what the port advertises via pullup-resistors. It may be 4.5W, 7.5W or 15W. You never know. Nice in theory, but none of the usb nvme adapters that I bought work reliably in any port for longterm use. They certainly don't work in any low power devices, like various ARM SBC USB ports because most of those use current limiting power switches for USB ports. And they don't work in my workstation reliably longterm either, for whatever reason. I guess you really have to be lucky to have a 15W Type-C data port. Funny how often these sell with Type-C <-> USB-A cables, though.

deleted 4y ago
[deleted]
TacticalCoder 4y ago
> Not sure how are these nvme enclosures supposed to work. Aren't there some with their own external power? If anyone has a brand/model to recommend I'm all ears.
rektide 4y ago
Peak power on these recent-ish high performance recent drive reviews shows 9w, but most drives peak consumption is 5W. https://www.tomshardware.com/reviews/samsung-990-pro-ssd-review/2 https://www.tomshardware.com/reviews/samsung-990-pro-ssd-rev... Absolutely some drives won't qualify, especially PCIe 5. But many will be fine. Also, PCIe 3 x4 is 4GBps or 32Gbps which isn't that far from saturating usb4 anyways, so it's not like we even can get drives running full tilt over USB at present. Many of these controllers probably top out at PCIe 3 or even less, if they don't support 40Gbps (most cheap-ish ones won't). Hopefully we start seeing some usb-pd capable systems & drives. The want to plug in 2 or 4 drive 3.5" enterprise drive arrays to my laptop & have it just work. Even just a single 3.5" of power would be so helpful. And it'd mean you could alternatively be charging your phone well too, which is probably the more common everyday ask.
- megous 4y ago
  5W is still a lot if you add controller power requirements, and 5V->3.3V DC-DC conversion losses. Also I have one of those Power-Z Type-C <-> Type-C power meters, and even with less power hungry western digital nvme, it didn't fit into 4.5W. And it consumed the most power not even during initial write test, but during a minute after kernel reported sync() success so after everything was supposedly written to the device and no power hungry activity was needed. Then it jumped to 7-8W. I guess these dram-less nvme's do some reshuffling from faster flash to slower flash locations during idle time. Which is probably terrible for portable use, where you may want to sync() and then unplug the device once the OS tells you everything is synced up. Creating regular power loss situations during these reshufflings just feels like putting too much trust into nvme firmware, IMO. :D
jeffbee 4y ago
The thing in the picture won't work at all if you plug it into a USB 3.0 port so that problem solves itself. I believe Thunderbolt ports are required to provide a minimum of 15W. But overall you might be right, there is not an end-to-end negotiation that would avoid a worst-case brownout of you had a very power-hungry SSD. The SSD in the article has a high-power active mode of 7.5W max (I am not sure why it says 3.3v*3.3A on the sticker[1]) and the TB controller in the enclosure claims 1.2W, so in this case it seems fine. It's possible to configure NVMe devices with power caps, but the 970 Evo in the article loses 95% of its performance if you cap it to 3.6W, which is its lowest operational power state. 1: Edited to say this is because mine is a 970 Evo Plus apparently the original really did draw that much current.
- megous 4y ago
  > It's possible to configure NVMe devices with power caps, but the 970 Evo in the article loses 95% of its performance if you cap it to 3.6W, which is its lowest operational power state. Heh, yeah I saw about 4 MiB/s max read speed with similar enclosure plugged into USB 3.0 port (I guess it self limited for a while). Meanwhile much less power hungry SATA SSD + USB-SATA bridge worked at 400 MiB/s there.
  - jeffbee 4y ago
    I don't know why the Samsung is so bad at low power. A WD SN850X in the same machine has no noticeable change in random read performance with a low power state configured. It's half the speed of the Samsung at full power, but 10x as fast at low power.

by megous 4y ago

deleted 4y ago

[deleted]

TacticalCoder 4y ago

> Not sure how are these nvme enclosures supposed to work. Aren't there some with their own external power? If anyone has a brand/model to recommend I'm all ears.

rektide 4y ago

Peak power on these recent-ish high performance recent drive reviews shows 9w, but most drives peak consumption is 5W. https://www.tomshardware.com/reviews/samsung-990-pro-ssd-review/2 https://www.tomshardware.com/reviews/samsung-990-pro-ssd-rev... Absolutely some drives won't qualify, especially PCIe 5. But many will be fine. Also, PCIe 3 x4 is 4GBps or 32Gbps which isn't that far from saturating usb4 anyways, so it's not like we even can get drives running full tilt over USB at present. Many of these controllers probably top out at PCIe 3 or even less, if they don't support 40Gbps (most cheap-ish ones won't). Hopefully we start seeing some usb-pd capable systems & drives. The want to plug in 2 or 4 drive 3.5" enterprise drive arrays to my laptop & have it just work. Even just a single 3.5" of power would be so helpful. And it'd mean you could alternatively be charging your phone well too, which is probably the more common everyday ask.

megous 4y ago
5W is still a lot if you add controller power requirements, and 5V->3.3V DC-DC conversion losses. Also I have one of those Power-Z Type-C <-> Type-C power meters, and even with less power hungry western digital nvme, it didn't fit into 4.5W. And it consumed the most power not even during initial write test, but during a minute after kernel reported sync() success so after everything was supposedly written to the device and no power hungry activity was needed. Then it jumped to 7-8W. I guess these dram-less nvme's do some reshuffling from faster flash to slower flash locations during idle time. Which is probably terrible for portable use, where you may want to sync() and then unplug the device once the OS tells you everything is synced up. Creating regular power loss situations during these reshufflings just feels like putting too much trust into nvme firmware, IMO. :D

jeffbee 4y ago

The thing in the picture won't work at all if you plug it into a USB 3.0 port so that problem solves itself. I believe Thunderbolt ports are required to provide a minimum of 15W. But overall you might be right, there is not an end-to-end negotiation that would avoid a worst-case brownout of you had a very power-hungry SSD. The SSD in the article has a high-power active mode of 7.5W max (I am not sure why it says 3.3v*3.3A on the sticker[1]) and the TB controller in the enclosure claims 1.2W, so in this case it seems fine. It's possible to configure NVMe devices with power caps, but the 970 Evo in the article loses 95% of its performance if you cap it to 3.6W, which is its lowest operational power state. 1: Edited to say this is because mine is a 970 Evo Plus apparently the original really did draw that much current.

megous 4y ago
> It's possible to configure NVMe devices with power caps, but the 970 Evo in the article loses 95% of its performance if you cap it to 3.6W, which is its lowest operational power state. Heh, yeah I saw about 4 MiB/s max read speed with similar enclosure plugged into USB 3.0 port (I guess it self limited for a while). Meanwhile much less power hungry SATA SSD + USB-SATA bridge worked at 400 MiB/s there.
- jeffbee 4y ago
  I don't know why the Samsung is so bad at low power. A WD SN850X in the same machine has no noticeable change in random read performance with a low power state configured. It's half the speed of the Samsung at full power, but 10x as fast at low power.