I'm currently traveling for months at a time and my homelab has become unreachable to me over VPN due to a unknown complication after a power outage.
Just as a learning experience for all, my mistake was that I set-up my VPN very far down the stack - as a wg-easy app inside TrueNAS SCALE's apps ecosystem. My very important reason for doing it was that way was that wg-easy allows for setting up client devices with a QR code...
Anyway, the NAS is not booting back up nor do the TrueNAS apps. I should've set my VPN up right at the front of the network - on my MikroTik router that also supports Wireguard. The funny thing is I was so happy that my NAS has IPMI and whatnot but now I can't even access it.
For now the NAS is kept powered on from what I know, it just doesn't boot. This should help prevent bitrot until I'm back. All important files are backed up on a 3rd party service.
It's a shame my Jellyfin and Navidrome inaccessible, but I'll live.
Now I'm thinking about buying an UPS so that this doesn't happen in the future. I'd like the UPS to be fanless and rackmount, so that limits me to ~700VA territory.
Devices in my homelab pull about 65W idle and spike to say 150W when everything is booting. ISP modem, router, POE+ switch, AP, NAS. I might add another 20W due to a Lenovo M920q in the future.
I only really care about NUT and graceful shutdown instead of long runtime on battery.
I was thinking about this: https://www.apc.com/us/en/product/SMT750RMI2U/
In my country I can get it with new batteries (no front panel) and a network card for NUT for a total of 180 EUR.
Would that work? Would you be afraid of leaving an UPS (it is kinda like a bomb after all) unattended an leaving your home for 6 months at a time?
If you can afford one, I would strongly recommend going with a dual-conversion UPS. A line-interactive UPS like the one you posted essentially acts as a pass-through for your mains power until it detects a power loss or a brown-out. This works most of the time, but there's a short delay during the switch from line to batteries (just guessing, but most likely on the order of milliseconds). This might not sound like much, but you're counting on the capacitors in your server's power supply to hold enough charge until the UPS kicks in.
The other thing to consider is that a dual-conversion UPS also supplies "clean" power to your equipment. It essentially acts as a DC power supply connected to an inverter, so regardless of how bad your input power is, you're always going to get the correct voltage and frequency out. I connected my old line-interactive UPS to a cheap generator at one point; the voltage and frequency regulation was so bad on the generator that my UPS continually switched on/off of battery (several times per second), and the equipment attached to it immediately shut down.
I can connect my dual-conversion UPS to the same generator, and it keeps humming along as if it was connected to mains voltage. According to the datasheet, anything from 60VAC to 150VAC, it's still going to output clean 120V/60hz power.
They're much more expensive. Mine is 1000VA, and if I remember correctly, I paid something like 600 or 700 USD for the UPS. An add-on rackmount battery pack was another $300 or so. It was well worth the cost, though.