@JS_racer Hmmm....I'm doing the same thing (mbentley software 5.8.4 on my Synology...I'll go see if I can get some stats on how much disk i/o is going on)

In the meantime, I have gone from software to hardware controller at my other site with no issues, but in that case the donor software controller was at a lower version than the OC200.  However, I have gone from software 5.6-> software 5.8 with the same backup, so you should be at least 99% ok going from software 5.8.4 back to hardware 5.7.6.

Since you have Docker anyways....you could try all all this by spinning up a 5.7 software controller, apply your 5.8.4 backup and see what happens.  If successful, you can always make a 5.7 backup from the temp software controller to apply to your OC200....or, with any luck, the 5.8.4 for the OC200 will pop up in the next week or three....

  @JS_racer 

At first glance my IOPS seem to peak in the 200/s range, however my NAS is doing nothing, and my Omada network is pretty quiet right now, and I'm just running OmadaSDN and PiHole as containers.  If you're generating so much data that your NAS is hammering away, you might be better to get yourself a USB->SATA adapter and a small cheap SATA hard drive and attach it to a USB connector on your NAS.  Let the small, quiet, slower 2.5" mechanical drive do the dirty for Omada solution...and it's probably the same price or cheaper than buying an OC200...and you don't have to worry about baking the internal flash drive in that after 6 months either ;)

Here's a 2-hr window during a quiet time on the NAS/network. My writes are consistently higher than reads...which could very well be the Docker SDN controller.