TrueNAS pool recovery
TrueNAS uses ZFS pools built from vdevs. The effect of a failed disk depends on whether that disk belongs to a mirror, RAIDZ group, special vdev, log, cache, or another role.
Understand the symptom
Redundancy is defined within vdevs, not across arbitrary disks in the pool. A special metadata vdev can be critical even when most data disks are healthy. Resilvering and scrubbing read broadly and write new state; they are maintenance operations, not source-preservation steps for a pool with multiple weak members or an uncertain failure sequence.
What you may see
The pool remains accessible but one or more devices have errors, are missing, or are being replaced.
A required top-level vdev or too many members may be missing for normal import.
Another member may be weak, causing the rebuild workload to expose additional unreadable regions.
Dataset keys, SED credentials, pool import, and filesystem availability are separate layers.
Protect the source
Replacing or detaching a current member can remove the last valid copy of required data.
Import options may change the pool state or discard recent transaction groups.
Broad reads can accelerate a disk that is already returning errors.
Do this now
Save pool GUIDs, vdev tree, device IDs, error counts, scan status, and recent alerts.
Preserve slot order plus removed, spare, replacement, special, cache, and log devices.
Keep dataset keys, passphrases, SED credentials, TrueNAS config exports, and host details.
If errors are increasing or a second member is unstable, preserve the devices before continuing broad reads.
NEPFOSYS process
NEPFOSYS maps vdev roles, redundancy, pool GUIDs, replacements, and the exact failure sequence.
Unstable devices are imaged individually with unreadable regions recorded.
ZFS metadata, transaction groups, datasets, encryption state, and priority files are evaluated from protected sources.
A clear next step
Start a case with the exact symptoms, incident timeline, prior attempts, encryption details, and the files that matter most. NEPFOSYS will route the case to the appropriate DFW intake or nationwide mail-in path.
Start with a case reviewQuestions, answered
Only when the remaining vdev members are healthy and the topology is certain. Multiple errors or weak members call for preservation first.
The role and state matter. Cache is normally noncritical, while special vdevs can contain essential metadata and some log configurations require careful handling.
It can help identify pools, shares, encryption settings, networking, and prior device assignments, so preserve it with the disks.
DFW local · Nationwide mail-in