u/chiefrussian

My external ZFS pool went offline after a power outage. The drive is connected via USB enclosure. I've tried recovery on both TrueNAS 25.04 and Ubuntu ZFS 2.2.2 with no success. Data is irreplaceable (no backup) so looking for any recovery options before going to professional recovery.

Drive Info

• Single disk pool, no redundancy
• Drive reads fine with dd at 200+ MB/s, no read errors
• SMART test passes

Pool Label (zdb -l /dev/sde1)

name: 'external_backup' state: 0 txg: 2893350 pool_guid: 5614369720530082003 txg from uberblock: 2894845

zdb -e -p /dev/sde1 on TrueNAS shows

vdev.c: disk vdev '/dev/sde1': probe done, cant_read=0 cant_write=1 spa_load: LOADED successfully then crashes at: ASSERT at cmd/zdb/zdb.c:6621 loading concrete vdev 0, metaslab 765 of 1164 space_map_load failed

All Import Attempts Fail With

cannot import 'external_backup': I/O error unable to open rootbp in dsl_pool_init [error=5]

What I've Tried

• zpool import -f
• zpool import -F -f (recovery mode)
• zpool import -F -f -o readonly=on
• zpool import -f -T 2893350 — gives different error: "one or more devices is currently unavailable" instead of I/O error
• zdb -e -p — pool loads but crashes at metaslab 765 space map verification
• Tried on TrueNAS 25.04 and Ubuntu ZFS 2.2.2/2.3.4

Key Observations

• cant_write=1 appears on TrueNAS but not on Ubuntu
• zdb actually loaded the pool successfully on TrueNAS before crashing at metaslab verification
• -T 2893350 (older txg from label) gives a different error suggesting that txg may be accessible
• partuuid symlink exists and matches label

Any suggestions on next steps before going to professional recovery?