Question Ubuntu 20.04 LTS NVMe Gen4 Speeds?

Jul 16, 2021
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Hello, I asked this question on Reddit but I also wanted to know if anyone here on Tom's Hardware could potentially know a solution. Thanks.

I built a system with an Intel i7 11700K along with that, I purchased a Samsung Pro 980 1TB NVMe drive. In Windows 10 testing the drive I am achieving the Gen4 speeds, with the crazy writes up to 7000 MB/s, but on Ubuntu with this drive, I notice the reads are maxing out about 4500 MB/s.
I wanted to know if this is something I should be concerned about or if there's something I can do about this? I'm just simply booting Ubuntu off of the drive, and setup everything the standard way.
Drive is using ext4
Tests:
  • hdparm -Tt /dev/nvme0n1
  • dd if=/dev/zero of=tempfile bs=1M count=4096 conv=fdatasync,notrunc status=progress oflag=direct
  • dd if=tempfile of=/dev/null bs=1M count=4096 status=progress iflag=direct
/dev/nvme0n1:
Timing cached reads: 40104 MB in 2.00 seconds = 20080.05 MB/sec
HDIO_DRIVE_CMD(identify) failed: Inappropriate ioctl for device
Timing buffered disk reads: 13632 MB in 3.00 seconds = 4543.33 MB/sec

root@server1:~# dd if=/dev/zero of=tempfile bs=1M count=4096 conv=fdatasync,notrunc status=progress oflag=direct

2640314368 bytes (2.6 GB, 2.5 GiB) copied, 1 s, 2.6 GB/s
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 1.62979 s, 2.6 GB/s
root@server1:~# dd if=tempfile of=/dev/null bs=1M count=4096 status=progress iflag=direct

4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 0.998495 s, 4.3 GB/s
 
7000 MB/sec is a CrystalDiskMark sequential reads 'brag number' for within Windows of course; but will not likely be seen often, save for when reading fairly small files...

As your speeds are clearly in PCI-e 4.0 territory, it might be hard to see the sorts of optimistic/elevated 'advertising-worthy' numbers you'd like to see in real world use.
 
Jul 16, 2021
2
0
10
0
7000 MB/sec is a CrystalDiskMark sequential reads 'brag number' for within Windows of course; but will not likely be seen often, save for when reading fairly small files...

As your speeds are clearly in PCI-e 4.0 territory, it might be hard to see the sorts of optimistic/elevated 'advertising-worthy' numbers you'd like to see in real world use.
Hi, thank you for your reply. I was testing within Samsung magician software on Windows - but I'm glad to know that the speeds are in the Gen4 range for Ubuntu, did not know if I was having an issue or not, and I'm just adopting into the NVMe world, coming from SATA. :)
 

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