[Solved] Very poor write performance with Samsung SM951 NVME on HFS+ with High Sierra

[dmrkillah]

Hi, I have updated directly from Sierra to High Sierra, chose to opt-out of APFS and stick with HFS+.

Everything went mostly fine, however I have noticed a very poor system perfomance, especially when writing data to disk. I ran Blackmagic speed test and the write speeds are only ~200MB/s while on Sierra they were about 1200MB/s.

The disk is SAMSUNG SM951 256GB M.2 NVMe (MZVPV256HDGL-00000).

The write speed also decreased from over 2000MB/s to 1700-1800, but that doesn't really bother me this much.

Any idea what might have caused that and can this be fixed somehow? Should I use a hacked NVMe Kext like in Sierra?

I am attaching the Problem Reporting files in the archive and a screenshot from Blackmagic test.

 

[RehabMan]

Should I use a hacked NVMe Kext like in Sierra?

Try using HackrNVMeFamily-10_12_6.kext and see what happens.

Note: You forgot to implement CPU PM.

 

[dmrkillah]

Thanks @RehabMan! After using hacked kext the result was the same, however it seems that it is my disk/motherboard issue as the same is now happening after return to Sierra

 

[olej7777]

Hi. I Have the same problem, very poor write on high sierra, any help?

 

[dmrkillah]

I ended up buying Samsung 960 EVO, put it in the M.2 slot and purchased an M2>PCI adapter and put Samsung 951 there. Both drives now run at mostly full speed on both Windows and MacOS.