Thank you for the helpful information and advice. I apologize for linking to ads. How I connect NVMe would affect performance. I see that my assumptions about the numbers are pretty naive. Looking at the specs for a pretty fast conventional hard drive, a Hitachi Ultrastar HUA723020ALA641 , many different numbers jump off the page: Interface transfer rate: 600MB/s Interface: 6.0 Gb/s Media Transfer Rate: 207 MB/s (max) My Results: $ sudo hdparm -Tt --direct /dev/sda /dev/sda: Timing O_DIRECT cached reads: 680 MB in 2.00 seconds = 339.83 MB/sec Timing O_DIRECT disk reads: 430 MB in 3.01 seconds = 142.78 MB/sec For the NVMe drive, I see that it is *up to* 3.2 GB/s, or 3200MB/s, and this may be "up-to" that speed.. I see also that this depends on many factors. So perhaps I ought to be happy with these results: Timing O_DIRECT cached reads: 2506 MB in 2.00 seconds = 1252.75 MB/sec Timing O_DIRECT disk reads: 5088 MB in 3.00 seconds = 1695.50 MB/sec I did not see, right of the bat, numbers that are comparable to Media transfer Rate. Comparing these numbers: 10X the "direct disk read" speeds is ok with me. I still don't understand what options would be best in /etc/fstab for the NVMe M.2 drive. I have noticed various conjectures and ideas about discards or trim. I don't want to damage the new unit through ignorance. Thanks. Alan On Mon, Jun 19, 2017 at 8:12 PM, Dragon ryu wrote:

2017/06/20 午前9:16 "Sean Greenslade" :

A couple of notes:

On Sun, Jun 18, 2017 at 10:21:33PM -0700, Alan E. Davis via arch-general wrote:

...

Hello everyone:

I built a new machine with a Samsung SSD 960 EVO NVMe <https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSE wjWxp_rk8nUAhWBfn4KHadiANoYABABGgJwYw&ohost=www.google.com& cid=CAESEeD2DLyQ7hEOLOBgSPqc9iEd&sig=AOD64_35gPrHU2xXVzC269P D9qfp0UjlwQ&ctype=5&q=&ved=0ahUKEwi6nZrrk8nUAhUE42MKHXAuDBsQww8ILA&adurl= Samsung SSD 960 EVO NVMe <https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSE wjWxp_rk8nUAhWBfn4KHadiANoYABABGgJwYw&ohost=www.google.com& cid=CAESEeD2DLyQ7hEOLOBgSPqc9iEd&sig=AOD64_35gPrHU2xXVzC269P D9qfp0UjlwQ&ctype=5&q=&ved=0ahUKEwi6nZrrk8nUAhUE42MKHXAuDBsQww8ILA&adurl= Samsung 950 EVO NVMe M.2 500GB component.

Please don't link to ads. A page like this is much more appropriate:

http://www.samsung.com/semiconductor/minisite/ssd/product/ consumer/960evo.html

...

Installation went swell. I was able to use bootctl (by whatever name), which seemed to be easier than using GRUB. (on the Manjaro wiki was found an extremely coherent discussion of this system). I have encountered no problems other than slow-ish (if one would call it that).

When I run hdparm to test the performance of this memory, it falls far short of the specification of 32 Gb/s.

Where did you get that number? All the specs I see for these drives show transfer rates in MB/s. You may have confused the read/write specs of the drive with the link speed of the NVMe / PCIe bus. The two are not the same.

Also note that the read/write speeds are spec'd as "up to" speeds, so they are not guaranteeing any minimum speeds. Perhaps I'm just jaded, but I would be happy to get anything close to a spec-sheet speed on consumer hardware.

...

I realize that the Linux kernel has recently included some code for the NVME drivers. There is also some question as to the best parameters to use in /etc/fstab.

That will depend entirely on the filesystem you choose. Also note that real-world filesystems rarely do perfectly sequential reads or writes, so your real world read/write performance will almost certainly be lower than any HDD test utility shows.

--Sean

Also, it is depends on "How you connect NVMe" and "How M/B handles it", also "what filesystem you use".

-- [I do not] carry such information in my mind since it is readily available in books. …The value of a college education is not the learning of many facts but the training of the mind to think. ---Albert Einstein "Sweet instruments hung up in cases. . . keep their sounds to themselves." ---Shakespeare, _Timon of Athens_

On 21-06-2017 19:51, Alan E. Davis via arch-general wrote:

For the NVMe drive, I see that it is *up to* 3.2 GB/s, or 3200MB/s, and this may be "up-to" that speed..

You should always be aware of the up to claims but it should be achievable, even if it is only for large sequential reads. Another thing you should check is how many lanes are actually connected or being used to communicate with the nvme ssd. I remember seeing (I think it was on anandtech but can't find the article) that for some nucs intel's firmware was not activating all lanes or was operating the lanes at reduced speed (can't recall exactly), so you might be hitting something similar. -- Mauro Santos