[arch-general] Samsung NVMe set up

[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=DChcSEwjWxp_rk8nUAhWBfn4KHadiANoYABABGgJwYw&ohost=www.google.com&cid=CAESEeD2DLyQ7hEOLOBgSPqc9iEd&sig=AOD64_35gPrHU2xXVzC269PD9qfp0UjlwQ&ctype=5&q=&ved=0ahUKEwi6nZrrk8nUAhUE42MKHXAuDBsQww8ILA&adurl=>Samsung
> SSD 960 EVO NVMe
> <https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwjWxp_rk8nUAhWBfn4KHadiANoYABABGgJwYw&ohost=www.google.com&cid=CAESEeD2DLyQ7hEOLOBgSPqc9iEd&sig=AOD64_35gPrHU2xXVzC269PD9qfp0UjlwQ&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