I think just sleeping the HDDs might get about the same result.
I have a couple systems with i3-7100U CPUs, with 2 sticks of RAM and an NVMe SSD they idle at about 1-2 watts booted up into Proxmox.
HDDs suck down a lot of power relative to that, about 5W each just sitting there spun up.
Unfortunately I haven't figured out a good option for sleeping drives that are part of a ZFS pool in proxmox, there's just too much going on with constant drive activity.
I have a couple systems with i3-7100U CPUs, with 2 sticks of RAM and an NVMe SSD they idle at about 1-2 watts booted up into Proxmox.
HDDs suck down a lot of power relative to that, about 5W each just sitting there spun up.
Unfortunately I haven't figured out a good option for sleeping drives that are part of a ZFS pool in proxmox, there's just too much going on with constant drive activity.