RAID can keep a NAS running after some drive failures, but it cannot replace a separate backup. To reduce the risk of losing years of files, keep an independent off-site copy, check data integrity where your system supports it, and plan for power and drive problems. The specific failure behind the first-person headline is not established here, so this guide focuses on documented risks and Synology guidance; details vary by NAS maker and model.
Why a NAS can lose files despite having RAID
RAID provides redundancy against certain drive failures; it is not an independent backup. It does not necessarily protect against accidental deletion, corruption, malware, theft, or a failed array. Synology warns that RAID crashes and hard-drive failures can still result in data loss, and recommends backing up to a separate destination: Synology’s NAS backup guidance.
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Snapshots are useful for rolling back to an earlier state, but a snapshot on the same NAS remains exposed to events that affect that device. A synchronized copy can also reproduce a damaged or deleted file. Synology distinguishes local multi-version copies from backups stored elsewhere in its backup guidance.
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Mistake 1: Treating RAID as the backup
Think of RAID as a way to maintain availability through some disk failures, not as a way to recover from every kind of data loss. The protection depends on the RAID layout and the failure; it does not create a historical, independent copy of your files.
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Keep a separate backup destination. That could be another device or an off-site service, depending on your requirements. If the backup is only a snapshot or another copy on the same NAS, it may not be available when the NAS itself is damaged or compromised.
Mistake 2: Keeping no independent off-site copy
Synology recommends the 3-2-1 backup strategy: three copies of data, on two storage mediums, with one copy off-site. The numbers describe a backup approach, not a failure-rate statistic. A local external drive can add a separate copy, but it remains vulnerable to fire, natural disaster, or theft affecting the same location. See Synology’s explanation of NAS backup and its data backup overview.
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Choose a backup by recovery needs
Before choosing a destination, check how independent it is from the NAS, whether it is off-site, whether it retains previous versions, what data and NAS settings it covers, and how quickly you could restore it. Also consider ongoing cost and whether you can recover files if the NAS itself fails. No single destination suits every recovery plan; a local copy can make restores faster, while an off-site copy addresses location-wide disasters.
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Checksums can help detect when data has changed or become corrupted, but detection is not a guarantee of repair. Synology says Btrfs can detect silent data corruption and may self-heal when good redundant data is available; if repair fails, an off-site backup may be needed. Its advice on checksum mismatch errors describes this distinction.
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Check support before enabling scrubbing or checksums
Synology recommends periodic data scrubbing, but availability and behavior depend on the NAS model, filesystem, RAID configuration, and whether advanced data integrity checksums are enabled for shared folders. Check the guidance for your exact model and configuration before relying on Btrfs features or assuming a scrub can repair a problem. Synology explains data scrubbing in DSM 7 and provides guidance on choosing a filesystem for a volume.
Reduce power and hardware risks
Synology lists unexpected power failure, drive problems, incompatible drives, and memory faults among possible causes of volume crashes. A compatible UPS that supports NAS shutdown signaling can reduce the risk of an improper shutdown during a power interruption; it cannot restore lost data. For Synology systems, consult its guidance on volume crashes and choosing a UPS. Hardware compatibility is model-specific.
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Verify that you can restore files
A completed backup task does not by itself prove that you can recover usable files. Periodically restore a selection of files from the independent destination to a safe test location, and confirm that they open as expected. Include the data and configurations that matter to you, and keep the restore path accessible if the NAS fails. This is a practical way to check recoverability without assuming that an integrity feature or a successful task report guarantees it.
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