I am trying to get a raid 10 running with LSI 9260-8i (IBM M5015) and 4 x Samsung 850 Pro 512GB SSDs.
The problem is, that the resulting sequential write performance is really bad (< 100MB/s). With raid 0, it is > 800 MB/s.
My system is a Dell Precision T5500 with 2 x Intel Xeon X5675 3,06 GHz 6 Core, 72 GB RAM, running proxmox 5.1-51 on debian stretch.
These are my raid-parameters:
Strip size 64 KB Read Policy: No Read Ahead IO Policy: Direct IO Default Write Policy: Write Through Default Access Policy: RW
Enabling Disk Cache makes no difference with the write performance.
I created a thin lvm on the raid 10 for storing raw-images with IO thread enabled. On a virtual machine, the read performance is > 800 MB/s and with raid 0, i don't have the problem with low write performance.
What might be the problem?