For internal disks, ZFS only have loader.efi [Except 4)]. USB memstick has no ZFS and has loader.efi in UFS. ======================================================================== Output of gpart show with USB memstick attached. Note) diskid/DISK-S21MNXAG821947P is ada1. => 34 2000409197 ada0 GPT (954G) 34 2014 - free - (1.0M) 2048 409600 1 efi (200M) 411648 1024 2 freebsd-boot (512K) 412672 1024 - free - (512K) 413696 20971520 3 freebsd-swap (10G) 21385216 10485760 4 freebsd-ufs (5.0G) 31870976 1968537600 5 freebsd-zfs (939G) 2000408576 655 - free - (328K) => 34 488397101 ada1 GPT (233G) 34 2014 - free - (1.0M) 2048 204800 1 efi (100M) 206848 1024 2 freebsd-boot (512K) 207872 1024 - free - (512K) 208896 20971520 3 freebsd-swap (10G) 21180416 16777216 4 freebsd-ufs (8.0G) 37957632 450439168 5 freebsd-zfs (215G) 488396800 335 - free - (168K) => 34 488397101 diskid/DISK-S21MNXAG821947P GPT (233G) 34 2014 - free - (1.0M) 2048 204800 1 efi (100M) 206848 1024 2 freebsd-boot (512K) 207872 1024 - free - (512K) 208896 20971520 3 freebsd-swap (10G) 21180416 16777216 4 freebsd-ufs (8.0G) 37957632 450439168 5 freebsd-zfs (215G) 488396800 335 - free - (168K) => 3 1617794 da0 GPT (1.9G) [CORRUPT] 3 1600 1 efi (800K) 1603 34 2 freebsd-boot (17K) 1637 1614112 3 freebsd-ufs (788M) 1615749 2048 4 freebsd-swap (1.0M) ======================================================================== 1) Boot from ada0 WITHOUT USB memstick and ada1 attached (single drive). >> FreeBSD EFI boot block Loader path: /boot/loader.efi Initializing modules: ZFS UFS Probing 6 block devices... probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: * supported (preferred) probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: * supported (preferred) done ZFS found the following pools: zsysS01 UFS found 1 partitions load: '/boot/loader.efi' spa: 'zsysS01', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) load: '/boot.config' spa: 'zsysS01', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot.config' on pool 'zsysS01' (2) load: '/boot.config' spa: 'zsysS01', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot.config' on pool 'zsysS01' (2) Starting '/boot/lodader.efi' in 5 seconds....... ======================================================================== 2) Boot from ada0 without USB memstick attached (2 drives). >> FreeBSD EFI boot block Loader path: /boot/loader.efi Initializing modules: ZFS UFS Probing 12 block devices... probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: * supported (preferred) probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: * supported (preferred) done ZFS found the following pools: zsysS02 zsysS01 UFS found 2 partitions load: '/boot/loader.efi' spa: 'zsysS01', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) load: '/boot.config' spa: 'zsysS01', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot.config' on pool 'zsysS01' (2) load: '/boot.config' spa: 'zsysS01', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot.config' on pool 'zsysS01' (2) Starting '/boot/lodader.efi' in 5 seconds....... ======================================================================== 3) Boot from ada1 without USB memstick attached (2 drives). >> FreeBSD EFI boot block Loader path: /boot/loader.efi Initializing modules: ZFS UFS Probing 12 block devices... probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: * supported (preferred) probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: * supported (preferred) done ZFS found the following pools: zsysS01 zsysS02 UFS found 2 partitions load: '/boot/loader.efi' spa: 'zsysS02', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) load: '/boot.config' spa: 'zsysS02', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot.config' on pool 'zsysS02' (2) load: '/boot.config' spa: 'zsysS02', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot.config' on pool 'zsysS02' (2) Starting '/boot/lodader.efi' in 5 seconds....... ======================================================================== 4) Boot from ada1 without USB memstick attached, and only UFS in ada0 has loader.efi (2 drives). >> FreeBSD EFI boot block Loader path: /boot/loader.efi Initializing modules: ZFS UFS Probing 12 block devices... probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: * supported (preferred) probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: * supported (preferred) done ZFS found the following pools: zsysS01 zsysS02 UFS found 2 partitions load: '/boot/loader.efi' spa: 'zsysS02', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot/loader.efi' on pool 'zsysS02' (2) Loading '/boot/loader.efi' from pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) Failed to lookup '/boot/loader.efi' (file not found?) Failed to load '/boot/loader.efi' load: '/boot/loader.efi' spa: 'zsysS01', devpath: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) Failed to find '/boot/loader.efi' on pool 'zsysS01' (2) Loading '/boot/loader.efi' from pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) Load complete Loading '/boot.config' from pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) Failed to lookup '/boot.config' (file not found?) Loading '/boot.config' from pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) Failed to lookup '/boot.config' (file not found?) Starting '/boot/lodader.efi' in 5 seconds...... ======================================================================== 5) Boot from da0 [USB memstick] (3 drives). >> FreeBSD EFI boot block Loader path: /boot/loader.efi Initializing modules: ZFS UFS Probing 17 block devices... probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(2) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(3) probe: . not supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(4) probe: + supported probing: pciroot(0x0):pci(0x1f,0x02):msg(0x12):hd(5) probe: + supported probing: pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00) probe: . not supported probing: pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00):hd(1) probe: . not supported probing: pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00):hd(2) vdev_read: failed dev: 0xdca13d30, id: 1, lba: 32, size: 114688, status: 2 dskread: failed dev: 0xdca13d30, id: 1, lba: 128, size: 8192, status: 2 probe: . not supported probing: pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00):hd(3) probe: * supported (preferred) probing: pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00):hd(4) probe: . not supported done ZFS found the following pools: zsysS01 zsysS02 UFS found 3 partitions Loading '/boot/loader.efi' from pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00):hd(3) Load complete Loading '/boot.config' from pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00):hd(3) Failed to lookup '/boot.config' (file not found?) Loading '/boot.config' from pciroot(0x0):pci(0x1d,0x00):usb(0x00,0x00):usb(0x01,0x00):hd(3) Failed to lookup '/boot.config' (file not found?) Starting '/boot/lodader.efi' in 5 seconds......