Error nfs_io

The server reported an I/O error

The server tried to read or write the disk and failed. That's a storage problem on the NAS, not a network one — check its storage health.

What this means

NFS status 5, EIO. The NFS layer is fine; the disk underneath returned an error. Treat this seriously — it’s often the first visible sign of a failing drive.

Check on the NAS

• Storage manager / pool health: Synology Storage Manager, QNAP Storage & Snapshots, TrueNAS Storage → pool status, Unraid Main → array. A degraded or errored volume explains this.
• USB drives that were unplugged or spun down. Re-plug and re-export.
• Encrypted datasets that are locked after a reboot (TrueNAS) — unlock them.
• Overlay or FUSE mounts (mergerfs, rclone mounts, Docker volumes) exported over NFS can return EIO when the backend is unavailable.
• Linux: dmesg | tail on the server shows the actual disk error.

From the app’s side

Nothing to fix. Reconnect after the storage is healthy.