APC UPS question about overloading during server boot

[sarjekemo]

I finally got a proper UPS in my homelab for my two main servers, my NAS and my Proxmox host (as well as the other core stuff like my cable modem, router, etc.) Altogether, this hardware maxes out around 560W at full tilt, and around 400W at idle. The UPS I got is an APC Back-UPS Pro 1000, which is rated for 600W maximum load. Running both servers at 100% CPU load does push right up against the load limit, but this is a rare occurrence.

Anyway, the thing I'm most concerned about is if I were to experience a full blackout sufficient enough to cause the UPS battery to drain. When the power is restored, both of the servers will power up at the same time, and their fans will spin up to maximum during the BIOS boot, which seems to happen every time the servers have lost AC power. When I was setting this up, I powered up only my NAS, and the watt usage shot up to 500W during the spin-up. After the fans spun back down the watt usage dropped to only 200W. I then powered on the Proxmox host and the watt usage shot up to 580W, and then settled back down to 360. (Adding the cable modem, router and switch brings the indicated wattage up to around 400.)

So, the problem is, if I have a blackout, and power is restored, both servers will spin up at the same time. Assuming that the Prox host uses 380W at powerup and the NAS uses 500W, that's 880W - far exceeding the maximum rating for the UPS. Now, this only will occur for around 30 seconds or so, until after the BIOS boot sequence has completed and the fans have spun down to normal operating speeds. But I'm concerned that overloading the UPS for that length of time might trigger some kind of overload protection even if AC line voltage is OK and will just power everything off, and it'll end up in a loop. As I've shown, staggering the power-ups keeps us under the limit (just barely) but I'm not sure how I'd accomplish that. (maybe a WoL packet from one server to the other...?)

Should I be looking at just getting a larger UPS for this issue, even though running at 900W is basically nonexistent other than when the servers initially power on? Or is there some other ideas that anyone has to address this possible concern?

[JonPro]

Hi @sarjekemo,

I would recommend getting a higher capacity UPS that is large enough to handle the inrush current if all the load will be turned on simultaneously specifically the SmartUPS product line that has controllable outlet groups if you wanted to have a delay in turning on the outlets to lessen the impact of the inrush current.