New system I've built has a dual 1U redundant PSU in it (it's a 4u rackmount case). Currently I have one of the PSUs connected to an APC backup ups that my old Synology NAS is connected to. Synology box is the master for that UPS and Unraid is the slave using NUT plugin.   Due to the fact the rating on that UPS is barely enough for the Unraid system and the wish for redundancy I am planning on getting a second ups for the other 1U PSU which would just have Unraid on it.