4 ms·

One of my favorite bits of hardware is a UPS. I’ve played with several over the years, from fancy server-grade rack-mount APC stuff to inexpensive edge stuff.

by amluto 6mo ago

One of my favorite bits of hardware is a UPS. I’ve played with several over the years, from fancy server-grade rack-mount APC stuff to inexpensive edge stuff. Without exception, downtime is increased by use of a UPS. I used to plug a server with redundant PSUs into the UPS and the wall so it could ride out UPS glitches. Even today, a UPS that turns itself back on after power goes out long enough to drain the battery and is then restored is somewhat exotic. Amusingly, even the new UniFi UPSes, which are clearly meant to be shoved in a closet somewhere, supposedly turn off and stay off when the battery drains according to forum posts. There are no official docs, of course.

kube-system 6mo ago
Sounds like crappy UPSes. Even the cheap old used eBay Eaton UPSes I have in my homelab have a setting for "Auto restart" and the factory default setting is "enabled". But even rackmount UPSes are more of an "edge" sort of solution. A data center UPS takes up at least a room.
- amluto 6mo ago
  I assume that datacenters UPSes are better, but I’ve never used one except as a consumer of its output. But I’ve had problems with UPSes that advertise auto-restart but don’t actually ship with it enabled. And that fancy APC unit was sold by fancy Dell sales people and supported directly by real humans at APC, and it would still regularly get mad, start beeping, and turn off its output despite its battery being fully charged and the upstream power being just fine (and APC’s techs were never able to figure it out either).
  - chrisandchris 6mo ago
    > I assume that datacenters UPSes are better [...] I don't know about specific datacenter models, but in our colocation there are humans available 24/7. So the UPS might not start after failure, but there's a human to figure it out.
    - amluto 6mo ago
      Most (all?) decent datacenters also have generators on site, and the intent is that the UPS will never run out of charge. So the fully-discharged case is an error and it might be intentional to require intervention to recover.
      - kube-system 6mo ago
        Yeah, some people treat UPSes as "backup power" but that's not really what they're intended for. Their intended purpose is to bridge the gap during interruptions... either to an alternative power source, or to a powered-off state.
        amluto 6mo ago
        Sure, but when you stick a UPS in the closet to power your network or security cameras or whatever for a little while if there is a power interruption, you expect: a) If the power is out too long for your UPS (or you have solar and batteries and they discharge overnight or whatever) that the system will turn back on when the power recovers, and b) You will not have extra bonus outages just because the UPS is in a bad mood.
        kube-system 6mo ago
        I completely agree with B. But alas, people love buying shitty cheap UPSes. But A is along the lines of the misconception that I'm referring to... There should be no such thing as "the power being out too long for your UPS". A UPS isn't there to give you a little while to ignore the problem, it's there to give you time to address it. Either by switching to another source of power, or to power off the equipment. Now, the reason that every UPS that supports auto-restart has it as a configurable option, is because you often don't want to do this for many reasons, e.g.: * a low SOC battery could not guarantee a minimum runtime for safe shutdown during a repeated outage * a catastrophic failure (because the battery shouldn't be dead) could be an indication of other issues that need to be addressed before power on * powering on the equipment may require staggering to prevent inrush current overload The whole use case of "I'm using the UPS to run my equipment during an outage" is kind of an abuse of their purpose. It's commonly done, and I've done it myself. But it's not what they're for. But also, if you want a UPS that auto-restarts -- they exist -- but you get what you pay for.

by amluto 6mo ago

kube-system 6mo ago

Sounds like crappy UPSes. Even the cheap old used eBay Eaton UPSes I have in my homelab have a setting for "Auto restart" and the factory default setting is "enabled". But even rackmount UPSes are more of an "edge" sort of solution. A data center UPS takes up at least a room.

amluto 6mo ago
I assume that datacenters UPSes are better, but I’ve never used one except as a consumer of its output. But I’ve had problems with UPSes that advertise auto-restart but don’t actually ship with it enabled. And that fancy APC unit was sold by fancy Dell sales people and supported directly by real humans at APC, and it would still regularly get mad, start beeping, and turn off its output despite its battery being fully charged and the upstream power being just fine (and APC’s techs were never able to figure it out either).
- chrisandchris 6mo ago
  > I assume that datacenters UPSes are better [...] I don't know about specific datacenter models, but in our colocation there are humans available 24/7. So the UPS might not start after failure, but there's a human to figure it out.
  - amluto 6mo ago
    Most (all?) decent datacenters also have generators on site, and the intent is that the UPS will never run out of charge. So the fully-discharged case is an error and it might be intentional to require intervention to recover.
    - kube-system 6mo ago
      Yeah, some people treat UPSes as "backup power" but that's not really what they're intended for. Their intended purpose is to bridge the gap during interruptions... either to an alternative power source, or to a powered-off state.
      - amluto 6mo ago
        Sure, but when you stick a UPS in the closet to power your network or security cameras or whatever for a little while if there is a power interruption, you expect: a) If the power is out too long for your UPS (or you have solar and batteries and they discharge overnight or whatever) that the system will turn back on when the power recovers, and b) You will not have extra bonus outages just because the UPS is in a bad mood.
        kube-system 6mo ago
        I completely agree with B. But alas, people love buying shitty cheap UPSes. But A is along the lines of the misconception that I'm referring to... There should be no such thing as "the power being out too long for your UPS". A UPS isn't there to give you a little while to ignore the problem, it's there to give you time to address it. Either by switching to another source of power, or to power off the equipment. Now, the reason that every UPS that supports auto-restart has it as a configurable option, is because you often don't want to do this for many reasons, e.g.: * a low SOC battery could not guarantee a minimum runtime for safe shutdown during a repeated outage * a catastrophic failure (because the battery shouldn't be dead) could be an indication of other issues that need to be addressed before power on * powering on the equipment may require staggering to prevent inrush current overload The whole use case of "I'm using the UPS to run my equipment during an outage" is kind of an abuse of their purpose. It's commonly done, and I've done it myself. But it's not what they're for. But also, if you want a UPS that auto-restarts -- they exist -- but you get what you pay for.