NVMe SSD Fast, but SATA SSD slow !

Hi,

I have a Supermicro X10SDV-8C-TLN4F (Xeon D1541 3Ghz 8 Core, 16 Threads) with 64Gb RAM running ESXI 6.5 U1.

1x SATA DOM for ESXi

4x SATA hard disks of various sizes

1x Samsung SATA SSD 850 PRO 2TB

1x Samsung NVMe SSD 960 PRO 2Tb

I am doing a write test to a 10G file.  I don't believe the results.  The NVMe seems too "good to be true" and the SATA SSD seems "too bad to be true".  I suspect that the SATA SSD is not performing.

I have done the esxcli system module set –enabled=false –module=vmw_ahci and rebooted, and I got a small performance increase.  But still not what I thought.

Test is to write a 10G file.

NVMe SSD 960 PRO 2Tb

[root@localhost:/vmfs/volumes/599bd559-ff0022f4-2abf-0cc47a7c09b4] time sh -c "dd if=/dev/zero of=test bs=16k count=640k conv=sync"

real    0m 14.32s

Samsung say "2,100MB/s Seq. Write"- ESXi disk monitor says about 1,100MB/sec.

SATA SSD 850 PRO 2TB

[root@localhost:/vmfs/volumes/5984ddf8-0e518991-7de5-0cc47a7c09b4] time sh -c "dd if=/dev/zero of=test bs=16k count=640k conv=sync"

real    5m 32.65s

Samsung say "Up to 520 MB/sec Sequential Write" - ESXi disk monitor says about 65MB/sec.

SATA Disk

[root@localhost:/vmfs/volumes/589566b4-b40e0cf2-8cac-0cc47a7c09b4] time sh -c "dd if=/dev/zero of=test bs=16k count=640k conv=sync"

real    13m 29.23s

So are these numbers real ?

Thanks

john