Synology and UPS

By and large I have been happy with the Synology purchase for the home NAS. While I would have had more fun with FreeNAS, my spouse is probably happy I went with the solution that did not require my tinkering or attention here and there frequently. It is also nice to have the Synology apps for iPhone/Android so that we do not have to deal with upload data to the magic cloud.

I did have my first scare with the NAS though, entirely my own fault! At the end of summer there was a power outage that took down everything in the house, including the NAS. I did not have it hooked up to any sort of UPS device at the time, so it went down hard. I could not access it over the network, so I went to look at it, and the Synology NAS just sat there flashing two blue status lights. After doing some google research I was concerned they might be the death indicator lights. I ended up having to pull out the disk drives, remove physical power from the NAS, and then reboot it. After some time the device recovered and I gracefully shut it down, replaced the disk drives, and then rebooted. It came back up, no data lost, and what a relief!

After that scare I decided that I really ought to get a basic UPS for the NAS. I did my homework and found that Synology supports UPS standards that communicate the status of the power supply from the UPS. On Synology’s website is a compatibility list with rather expensive devices and even some dated devices. However, more google research said that any standards-compliant device should work. Of course, being primarily a Linux / Mac user, one could excuse me for balking at that idea when it comes to consumer grade computer equipment!

I really did not need a fancy UPS with lots of features. I just wanted a simple UPS device that will inform the Synology NAS when it switches over to battery. Ideally the UPS would use USB, since EIA-232 Serial Ports are not on Synology devices. I am not looking for a device that will keep a computer running for some amount of time, I simply want to keep the NAS and perhaps a network switch up and running long enough to safely shutdown.

After reading the Wirecutter recommendation for the CyperPower CP685AVR UPS, I searched around some more with google. I did not find any definitive information about Synology NAS devices working with this UPS model, but I decided to take the plunge and see if it would work since my local Microcenter store carries the UPS in stock. I really like the size of the UPS, it is about the size of a small shoe-box or a Cisco Press textbook. It also doesn’t make any noise which is always nice!

Safe Shutdown Test

Before hooking up the NAS to the UPS for power, I decided to try an experiment to make sure the UPS would work with my NAS.

  1. Keep Synology NAS powered by A/C power, but connect the UPS USB cable to the back of the NAS, and power on the UPS
  2. Switch off the UPS outputs only and see how the NAS handles the event.
  3. Switch on the UPS outputs, and then after a minute remove A/C power supply to the UPS
  4. Wait for safe shutdown time, and then confirm the NAS safely powers down.



Configuration was probably the easiest thing I have ever seen. In the Synology NAS control panel, in the Hardware and Power section, one simply navigates to the UPS tab. Place a check mark in the Enable UPS support box, and then set the safe mode timer. For now I have set this timer to 5 minutes. There is also a button “Device Information” at the bottom of the tab, and as shown in the above screen capture, the NAS automatically detects the UPS.

Test Results

Starting at the bottom and working up with the messages in the screen shot, all of the power events are stored in the NAS log file.  After enabling the UPS support, the NAS logs that the service started and identifies a UPS on the USB port. The message “Local UPS was plugged out” refers to step 2 of my simple test, where I kept the UPS plugged into A/C power but simply disabled the UPS outputs. After 5+ minutes, the NAS was still online and did not shutdown. Next, I re-enabled the power outputs on the UPS, and after a minute or two, removed A/C power from the UPS. The NAS logs that the UPS has gone to “battery” and the safe shutdown timer begins.


After the safe shutdown timer expires, the NAS shuts down the Cloud Station service, and logs a message stating it will be going into Safe Shutdown. At this point, keep in mind the NAS is still plugged into A/C power. After the NAS shuts down, the Status LED on the NAS was cleared, and I was no longer able to navigate the NAS via its web interface. I reconnected the UPS to A/C power, and after a minute or two, the blue lights on the NAS began to flicker. A few minutes later, the NAS was back up online and I was able to access to the web interface. Success!


The CyberPower CP685AVR UPS and Synology NAS work just as I had hoped–I could not be happier. I have read that some UPS devices will initiate periodic self-checks than can cause some NAS devices to think power has been lost. I will have to keep an eye out for this, and worst case I may need to extend the safe shutdown timer from 5 minutes to something longer. However, this UPS claims up to 70 minutes on an iMac G4, and I am sure that this NAS with its low-power ARM CPU will not exceed the power draw of an iMac G4. As such, there appears to be plenty of margin to work with.


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