Hello there,
I got an issue utilizing a set of Samsung PM871 SSDs in Openmediavault. The system is a a dual Xeon 2680v2 build with 8*16gb ram, using two Broadcom 2308 SAS controllers in jbod mode and two supermicro BPN-SAS2-826EL1 expander backplanes.
I am succesfully running 12 HGST Ultrastar 7k6000 in Raid z2 using zol, which gives better than expected performance.
However, I wanted to add a 6 disk mdadm raid0 with ssds for fast operations to do some quick multi node mpi work on them, where data consitency is less of a concern. As clients are all connected via FDR Infiniband I can make use of faster speeds, although the SAS Controller is becoming a bottleneck.
Unfortunally the SSDs are slower than the spinning disks in this particular system, which seems to be a software issue. Even with large block sizes the maximum write speeds are consistently at 82mb/s, while reads behaving as expected. Even with small block sizes the spinning disks are faster. I dont have this issue with a set of Samsung 850 pros i tested and not with some cheaper intenso ssds. Testing the drives in another system gives the expected write speeds and booting an arch linux from usb stick on the openmediavault system I get much faster writes too.
I am kind of clueless at the moment. Any idea what to do about that?
I am running Kernel 4.19.16-1, the arch stick I tested was also build with a 4.19.x Kernel. The system was set up utilizing a basic debian installation and the openmediavault repo.
Thank you in advance!