Just reporting some information in the hopes that others find it useful.
System:
ASRock Z490M-ITXac
Intel Core i3 10100 s1200
4x12TB Toshiba HDDs (CMR & 5 year warranty)
16GB Corsair DDR4 Venagance 2666 RAM
Noctua Cooler NH-LPi low profile cooler
Fractal Design Node 304 code (space for 6 HDDs)
Samsung EVO 950 512GB SSD (proxmox, nas boot and nas ssd cache)
Software:
Proxmox 6.2-1 OS for VM's and Docker Containers
HostAPD for a Wireless access point using the built-in WiFi card on the motherboard.
Config:
PCIe Passthrough for the HDDs to the NAS VM. 48TB RAID-5.
2x 32GB Virtual SSDs for NAS Cache
1x 16GB Virtual SSD for NAS apps.
VM Config
args: -device 'nec-usb-xhci,id=usb-ctl-synoboot,addr=0x18' -drive 'id=usb-drv-synoboot,file=/var/lib/vz/template/iso/synoboot_ds918_1.04-vm-xpenology1.img,if=none,format=raw' -device 'usb-storage,id=usb-stor-synoboot,bootindex=1,removable=off,drive=usb-drv-synoboot'
balloon: 0
bios: ovmf
bootdisk: sata0
cores: 2
efidisk0: local-lvm:vm-100-disk-1,size=4M
hostpci0: 00:17,pcie=1
ide2: none,media=cdrom
machine: q35
memory: 2048
name: xpenology1
net0: e1000=D2:F2:B8:6B:D0:40,bridge=vmbr0,firewall=0
numa: 0
ostype: l26
sata0: local-lvm:vm-100-disk-2,size=16G,ssd=1
sata1: local-lvm:vm-100-disk-3,size=32G,ssd=1
sata2: local-lvm:vm-100-disk-0,size=32G,ssd=1
scsihw: lsi
serial0: socket
smbios1: uuid=3964d1cc-e350-4fb3-b133-6903f5f05d7e
sockets: 1
vmgenid: c7f7222e-5bc7-4928-b6d1-6e0cd94f24d2
A personal note to Synology marketing - If you hadn't dropped Wireless AP support from the new DSM/NAS systems I'd have upgraded my existing DS415+ to a DS920+ That and the C2000 CPU-of-death issue.
What didn't work:
* Single SATA VM backed by a ZFS pool - It worked, i.e. you could create a simple volume in the running NAS on the ZFS pool, but proxmox only showed 22TB available capacity for a RAIDZ1 ZFS pool instead of the expected 30.64GB (48TB-12TB=36-overhead=33.6TB (30.64TiB). The pool is correct, (when using zpool list and zfs list) but when you add an SATA disk to the VM it shows the wrong capacity. - https://wintelguy.com/zfs-calc.pl
root@proxmox:~# zfs list
NAME USED AVAIL REFER MOUNTPOINT
tank 30.7T 33.8M 140K /tank
tank/vm-100-disk-0 30.7T 30.6T 69.6G -
root@proxmox:~# zpool list
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
tank 43.6T 95.9G 43.5T - - 0% 0% 1.00x ONLINE -
root@proxmox:/tank# zfs list -o space,compressratio,recordsize,volblocksize -r -t all
NAME AVAIL USED USEDSNAP USEDDS USEDREFRESERV USEDCHILD RATIO RECSIZE VOLBLOCK
tank 33.8M 30.7T 0B 140K 0B 30.7T 1.11x 128K -
tank/vm-100-disk-0 30.6T 30.7T 0B 69.6G 30.6T 0B 1.11x - 8K
* The DSM3615/DSM3617 synoboot 1.03 images. They boot in the VM, there is some disk activity but no output on the VM console or VM serial console. The DS419+ boots fine.
* Changing the VM from i440 to q35 re-orders the HDD ID's inside the NAS and kills the RAID-5 array. I was inititally using PCI passthough, two of the 4 drives were no-longer detected. The solution appears to be to re-upload the synboot image to the VM, delete all the SATA VM attached disks and re-create them all...
* Trying to re-install the VM was a 6 hour headache, I was getting Error Code 13 on re-install onto fresh disks, deleting an re-uploading the synoboot image fixed that - as detailed here.