5 ms·

The USB is limiting this so much there is no need to go with NVME over SATA, IMHO. I see the USB3 result for the "M.2 SSD" (I assume the author means SATA?) be

by kup0 6y ago

The USB is limiting this so much there is no need to go with NVME over SATA, IMHO. I see the USB3 result for the "M.2 SSD" (I assume the author means SATA?) being ~30/MB but almost surely something is going wrong there. That is not a normal result for any mid-to-high level SATA SSD. Plenty of SATA M.2 SSDs can easily hit the same speeds the NVME drive is hitting (specifically when on USB3). NVME might give you some additional random r/w performance, however. It seems like overkill to use NVME on USB 3.0 when SATA can saturate that bus just as easily. SATA M.2 drives will also run cooler. Some NVME USB controllers are notoriously hot-running

emidln 6y ago
Power consumption would be my guess for why one would choose NVME over SATA in this application.
- kup0 6y ago
  Hrm, maybe over USB it's different because of the performance limitations, but my understanding was that SATA was lower power draw. Though maybe I'm wrong and/or potentially this differs on a per-drive/per-controller basis.
  - wtallis 6y ago
    It very much depends on the particular drive, with both controller and NAND choice affecting power draw and efficiency. On a performance per Watt basis, most M.2 NVMe SSDs are much more efficient than M.2 SATA SSDs. The most efficient M.2 NVMe SSDs are also at least competitive with M.2 SATA SSDs in terms of absolute power consumption, despite outperforming the SATA SSDs by at least a factor of 2-3x. Power consumption from a M.2 NVMe SSD will also drop slightly when only one or two of its four PCIe lanes are used, which is the case when the drive is behind a USB to NVMe bridge. For example, comparing a SK hynix NVMe drive against of dozens of other M.2 NVMe and 2.5" SATA drives: https://images.anandtech.com/doci/16012/rr-all.png https://images.anandtech.com/doci/16012/rr-all.png Unfortunately, I don't think there are any M.2 SATA results in there, and those are often a little bit more efficient than their 2.5" counterparts (running off 3.3V rather than 5V, but stepping it down to at least one or two lower voltages on the drive in either case).

by kup0 6y ago

emidln 6y ago

Power consumption would be my guess for why one would choose NVME over SATA in this application.

kup0 6y ago
Hrm, maybe over USB it's different because of the performance limitations, but my understanding was that SATA was lower power draw. Though maybe I'm wrong and/or potentially this differs on a per-drive/per-controller basis.
- wtallis 6y ago
  It very much depends on the particular drive, with both controller and NAND choice affecting power draw and efficiency. On a performance per Watt basis, most M.2 NVMe SSDs are much more efficient than M.2 SATA SSDs. The most efficient M.2 NVMe SSDs are also at least competitive with M.2 SATA SSDs in terms of absolute power consumption, despite outperforming the SATA SSDs by at least a factor of 2-3x. Power consumption from a M.2 NVMe SSD will also drop slightly when only one or two of its four PCIe lanes are used, which is the case when the drive is behind a USB to NVMe bridge. For example, comparing a SK hynix NVMe drive against of dozens of other M.2 NVMe and 2.5" SATA drives: https://images.anandtech.com/doci/16012/rr-all.png https://images.anandtech.com/doci/16012/rr-all.png Unfortunately, I don't think there are any M.2 SATA results in there, and those are often a little bit more efficient than their 2.5" counterparts (running off 3.3V rather than 5V, but stepping it down to at least one or two lower voltages on the drive in either case).