I bought two identical Intel DC S3500 480GB SSDs with the intention of setting up a mirrored internal boot pool with the remaining capacity as a data pool. Internal boot is working on one drive, but I have not been able to get the second drive to join.

Initially the setup ran while the system was still in Legacy/CSM mode, so efibootmgr failed with rc=2 (no EFI variables). After switching the BIOS to UEFI, I ran the setup again. It completed, but reported efibootmgr failed for /dev/sdg (rc=5).

zpool status
  pool: flash
 state: ONLINE
        NAME        STATE     READ WRITE CKSUM
        flash       ONLINE       0     0     0
          sde3      ONLINE       0     0     0

df -h /boot
flash/boot       15G  2.6G   13G  18% /boot

The second SSD (sdg) has never been partitioned:

lsblk -o NAME,SIZE,FSTYPE,LABEL /dev/sde /dev/sdg
sde    447.1G
├─sde1     1M
├─sde2   510M vfat       EFI
├─sde3  15.5G zfs_member flash
└─sde4 431.1G
sdg    447.1G

Really would like the 2 drives to function properly and have the extra capacity.

helder-diagnostics-20260815-1101.zip

Edited yesterday at 09:02 AM1 day by H3LD3R7

Try this: stop the array, unassign the device that is not part of the pool, start the array, stop the array, reassign that device to the pool, start the array, post new diags.