Power Outage Caused Reboot

[NicCrockett]

We had a power outage this morning that caused our FreeNAS server to reboot. The power outage lasted a matter of a few seconds and the FreeNAS server is connected to a APC UPS with good working batteries. None of the other servers on the UPS went down and the UPS isn't set-up to shutdown the server if the power goes out. Is there a setting in FreeNAS that would cause the server to shutdown if there is a power outage? I've never set one if there is so it would have to be a default setting. Can someone point me to why this would have happened? I'm running FreeNAS Build: FreeNAS-9.3-STABLE-201602031011.

Thanks,
Nic

 

[m0nkey_]

If you have enabled the UPS service, the default is to shutdown within 60 seconds of mains power failing.

 

[hugovsky]

Could it be the transition time? what model/brand is your ups and your psu?

 

[NicCrockett]

The UPS service is turned off, but great thought.

My UPS is an APC Smart UPS 1500VA model number SUA1500RM2U. I'm not sure about the servers PSUs. I can tell you it's a Dell PowerEdge 2950 server. Here's a link to an Amazon listing for one that matches this server. Does this give you the info you need?

 

[hugovsky]

I was asking because some PSU need a shorter switch time. That and if the server is heavily used, it could trip the reboot.

 

[NicCrockett]

It's heavily used at night because it's our backup NAS. All of our servers backup to it at night. However, at the time of the power outage nothing would have been writing to it.

 

[hugovsky]

I can't find info on your PSU, but for the UPS, I've found this:

Transfer Time: 2ms typical

 

[jgreco]

We had a power outage this morning that caused our FreeNAS server to reboot. The power outage lasted a matter of a few seconds and the FreeNAS server is connected to a APC UPS with good working batteries. None of the other servers on the UPS went down and the UPS isn't set-up to shutdown the server if the power goes out. Is there a setting in FreeNAS that would cause the server to shutdown if there is a power outage? I've never set one if there is so it would have to be a default setting. Can someone point me to why this would have happened? I'm running FreeNAS Build: FreeNAS-9.3-STABLE-201602031011.

Thanks,
Nic

Did it voluntarily reboot? What do the logs indicate?

Just so you know, a heavily loaded server such as a NAS ... especially with a poorly sized power supply (read "The Importance of Clean Power") ... can easily be unable to cope with the wild power spike that can result from this sort of thing. A high quality, somewhat oversized PSU is the go-to answer for part of the problem, and a UPS that can easily start shouldering the load during a failure is the other part of the problem.

You should be able to yank the power on the UPS and plug it back in, several times in rapid succession (half second, several seconds, etc) without anything happening to the server. If not, your power setup sucks and needs to be addressed. Your power company will not be kind to you when a tree falls on the feeder, so be a little aggressive about testing.

 

[cyberjock]

To add to what jgreco said, some PSUs don't take kindly to having power is is the "simulated sine wave" that is more of a square wave. Older and/or cheaper PSUs and UPSes often don't mix well. Last I read, if your using one of those 80+ Gold or Platinium certified PSUs they are more susceptible to problems with UPS power that isn't a good sine wave. I've seen this and the fix for me was to buy a new PSU (it was cheaper than buying a new UPS).

 

[jgreco]

To add to what jgreco said, some PSUs don't take kindly to having power is is the "simulated sine wave" that is more of a square wave. Older and/or cheaper PSUs and UPSes often don't mix well. Last I read, if your using one of those 80+ Gold or Platinium certified PSUs they are more susceptible to problems with UPS power that isn't a good sine wave. I've seen this and the fix for me was to buy a new PSU (it was cheaper than buying a new UPS).

The APC SUA1500RM2U is actually a ""sine wave"" model. They're not the total crap of a low end UPS but they're also not the absolute best-est.

As a long time buyer of APC (show of hands, anyone with over 100 units?) I can tell you that especially with the older APC designs I've seen units that just can't shoulder a sudden load transfer. Batteries show as good, unit load's 60%, utility failure, BAM, voltage sag while it transfers to battery. Then everything's fine. Of course, that's useless and stupid as a UPS.

We discovered that we actually had to load test each unit back in the 1990's, and some units just couldn't survive. Put a heavy load (space heater, bunch of 100W light bulbs, whatever) on the unit and then also a scope.

 

[NicCrockett]

The load based on the lights on the front of the UPS is 2 of 5 so in theory it's not overloaded. Obviously the load is higher when devices are starting up, but the only device that restarted this morning during the power outage was the FreeNAS server.

 

[jgreco]

Yeah, I believe you, I'm just throwing stuff out there. Might still be worth testing for, if you can't figure out some other answer.

 

[NicCrockett]

I appreciate the ideas. I realize you can't see what's going on in my environment so all you can do is throw something out there and hopefully it's helpful. I'll be honest power isn't my strong suit. Some of the stuff you guys have mentioned has gone over my head. Things like transfer time and sine wave I don't know how they translate in the larger picture so you guys might be on to something and I wouldn't know it. I am doing research to try to figure it out, but I don't have high hopes. I do appreciate all of help even if it doesn't pan out.

 

[jgreco]

Honestly, if you don't understand something, come back and ask more. Or Google the heck out of it.

The transfer time is the amount of time it takes a UPS to recognize mains power has failed, and to switch over to generating from battery. This happens on any "standby" UPS, because the unit is only standing by to generate power. It is very power efficient. A "double conversion" UPS is always providing power from its batteries, and the AC line is powering a charger that charges them in real time. This means that if the AC power is lost, there's no interruption where the UPS has to switch over to battery.

Sine wave refers to the shape of the AC power. Cheap UPS's generate something that's merely intended to kinda-work.