Hi.
Here's mine which works fine for me:
args: -device ich9-usb-ehci1,id=usb,multifunction=on,bus=pci.0,addr=0xa -drive file=/mnt/pve/templates/template/qemu/synoboot-test.qcow2,format=qcow2,if=none,id=drive-usb-disk2,cache=writeback -device usb-storage,bus=usb.0,port=2,drive=drive-usb-disk2,id=usb-disk2,bootindex=1,removable=off -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-hpet -global PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1 -realtime mlock=off -machine pc-i440fx-2.9,accel=kvm,usb=off,vmport=off,dump-guest-core=off -cpu kvm64,+kvm_pv_unhalt,+kvm_pv_eoi
boot: nc
bootdisk: sata0
cores: 2
cpu: kvm64
memory: 1024
name: test
net0: e1000=A6:F0:EF:B7:91:45,bridge=vmbr0
numa: 0
ostype: l26
sata0: local-lvm:vm-114-disk-1,size=10G
smbios1: uuid=2dce823b-ffd0-44e5-8914-57feab9873a1
sockets: 1
tablet: 0
vcpus: 2
vga: qxl
Of course, you have to change the path to your synoboot image file. I use the qcow2 format, just as it's a bit smaller. Otherwise you can use the synoboot.img file directly. Just rename the suffix to '.raw' as already mentioned.
I currently run 6 different virtual xpenology machines on just one tiny NUC (with 16GB memory) in a Proxmox cluster. The harddrives are mounted indirectly via iSCSI with the help of Proxmox' storage manager. No RAID inside the machines. RAID is already done on the iSCSI target side.
I'm totally happy with this setup. Far more better than running XPenology on baremetal, like my old ReadyNAS.