Hope someone can help: Have tiny home server/router with two USB SSDs forming a ZFS mirror. Also each disk has swap and ESP partition. One disk seems to die now (dmesg says usb 3-1: device not accepting address). Even though ZFS should give redundancy, the system becomes unresponsive. Boot loader is on the dying disk. Adding the mountpoint on the second disk does not have effect after rebuild and reboot:

          ESP = {
            size = "512M";
            type = "EF00";
            content = {
              type = "filesystem";
              format = "vfat";
              mountpoint = "/boot-fallback";   # added
              mountOptions = [ "umask=0077" ]; # added
            };
          };

Do I need to do something extra after changing the disko.nix file (adding the two lines above)?
I want to get redundancy for the bootloader. Do I need grub for this (used systemd-boot so far)?