[TriLUG] AMD Rizen

[Jeffery Painter via TriLUG]

Hi Dwain,

Thanks for the tip!

I did some more testing (copying lots of large files, removing files, 
etc) am getting the expected speed/performance out of this drive.

It was my mistake that I ordered a Samsung 850 EVO and the read/write 
performance on that particular model is limited to 540 MB/s on both read 
and write operations.  I had just assumed all NVMe drives were created 
equal, but that is definitely not the case.

I just ordered a Gen3 x4 NVMe which reportedly can do 2.6Gb/s read and 
1.3Gb/s write - much better.  I am doing a large number of MySQL 
transactions and will be interesting to see how much this helps.  I 
think for the primary OS/boot drive, the Samsung is fine.  Luckily my 
new board has two M.2 slots, so I will see if I can just migrate the 
database files over to this new drive when it arrives.



On 04/18/2017 01:03 PM, Dwain Sims via TriLUG wrote:
> Jeff:
>
> Be a little careful it reading too much into performance data you might be
> getting out of hdparm.  Determining read performance of SSDs can be tricky
> at times when trying to do a benchmark.  You can wind up reading data that
> is not really there, and you will get higher performance readings than you
> would really expect to see in real life. (which could be happening on the
> SATA device)  Many devices are smart enough to determine that you are
> trying to read "empty" blocks, and will just return zeros or random garbage
> and not actually bother reading the actual blocks.
>
> Give "fio" (the flexible io tester) a try.  And make sure you set up a file
> or partition and pre-condition it first, by writing random data all over
> the test file or partition before you try to read it back.
>
> https://github.com/axboe/fio
>
> hdparm may not be that sophisticated when dealing with SSDs.
>
> This is not to say that you are not having a NVMe performance issue.  But
> you might not!
>
> You might also want to check and see if Samsung has specific drivers for
> this NVMe device.  Sometimes the in-box drivers are not as good as what the
> manufacturer releases for a specific device.  The in-box drivers are
> getting better, but there are still some exceptions.
>
> Dwain

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Jeff Painter

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