I have Proxmox 5.1. Xpenology 1.02b loader;  DSM6.1.4 Update 5.    Intel onbard (AHCI) SATA controller passthrough.  I have 3 SSD in RAID0 mode.  What I notice is, the write performance on SSD is terrible.  I've try to tweak Proxmox, and the Xpeno VM, but nothing seems to help.      My VM config: args: -device 'piix3-usb-uhci,addr=0x18' -drive 'id=synoboot,file=/var/lib/vz/images/100/synoboot_jun2b_virtIO.img,if=none,format=raw' -device 'usb-storage,id=synoboot,drive=synoboot' bios