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 <knight.ryu12@xxxxxxxxx> wrote: > > > 2017/06/20 午前9:16 "Sean Greenslade" <sean@xxxxxxxxxxxxxxxxxx>: > > 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_
