Failed TrueNAS Mirror: Dataset Visible but Files Will Not Open or Extract
TL;DR:
To recover files from a failed TrueNAS ZFS mirror built on virtualized WD EX2 iSCSI volumes, you must create a sector-level image of the surviving drive before attempting any automated rebuilds.
● Replacing the failed disk will trigger an automatic TrueNAS resilver that can wipe the replacement drive and permanently damage the complex underlying Proxmox storage stack.
● Do not initialize or rewrite the surviving drive to force recognition, as seeing the dataset tree without file access indicates a topology failure rather than a standard file deletion.
● Recoverit NAS Recovery cannot reconstruct a broken ZFS or iSCSI topology and functions only if the affected pool or dataset is already imported and exposed as readable storage.
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In this failed-mirror recovery case, two WD EX2 JBOD volumes were exposed through iSCSI to Proxmox and then mirrored by TrueNAS as an unencrypted ZFS dataset. One physical drive failed, the other still worked, and several recovery tools could see the volume and dataset structure but could not extract the files. That layered setup is not an ordinary deleted-folder case.
Do Not Rebuild or Resilver Before Preserving the Existing State
TrueNAS documentation says replacing a failed pool disk automatically triggers a resilver, and a replacement disk can be wiped as part of the process. In a recovery situation where the current layout is already difficult to read, preserve the original devices and configuration before starting replacement or rebuild operations. If possible, create sector-level images or clones of readable members and work from those copies; byte-to-byte imaging guidance explains why preserving the source before repeated scans or repair attempts is safer.
TrueNAS disk-replacement guidance is appropriate for a healthy redundant pool; it should not be treated as a data-recovery shortcut when the pool or backing storage cannot reliably serve the files.
The Healthy Disk Does Not Automatically Make the Files Easy to Extract
The surviving HDD is important, but the data path here still includes the WD EX2 volume, iSCSI mapping, virtualized TrueNAS, and ZFS mirror. Seeing the dataset tree without being able to open files may mean the obstacle is in that storage stack rather than simple file deletion. Avoid converting, initializing, or rewriting the surviving member just to make a recovery tool recognize it.
When Recoverit NAS Recovery Fits
Recoverit NAS Recovery is relevant when the NAS volume or exported data remains reachable and stable enough to scan. Recoverit's current ZFS guidance also requires the affected pool, dataset, or logical volume to be imported, mounted, or otherwise exposed as readable storage. It should not be used as a substitute for reconstructing a broken iSCSI/ZFS topology or imaging a physically failing disk. If the only useful copy depends on the unstable member, stop repeated scans and use a recovery lab familiar with NAS, ZFS, and iSCSI.