After moving most of my server functions from VMs running on a Synology DS218+ to VMs running under Proxmox on an HP 800 G3 Mini-PC, it seemed a good idea to use a share on the DS218+ to store VM backups and .iso images.
Mounting CIFS/SMB shares Proxmox is straightforward, and while the use of this share didn’t present specific problems, the HDD used just wouldn’t spin down, despite enabling the corresponding power management option in the Synology DSM control panel.
As it would turn out, this seems to be a fairly common issue, with Proxmox regularly accessing the share and preventing the associated drive from spinning down.
The solution (or rather, the workaround that fit my usecase) turned out to be to change the share type from CIFS/SMB to NFS: using this protocol, no similar access pattern was observed, leading the drive to successfully spin down when possible:
This made it possible to cut a half dozen or so watts from the average power consumption of my “minilab” of sorts, due to the drive being a fairly power hungry 7200 RPM mechanical hard disk.