What to do if…

The NAS is not responding

An unreachable NAS is diagnosed like a server: network first, disks next, external copy in parallel. The internal RAID is not repaired by pulling out disks at random: as long as a copy outside the NAS exists, that copy is the path to restoration, and tinkering with the disks is the path to permanent loss.

Updated October 20263 min read5 sources cited

Key points

Network first: another workstation, the admin interface, another cable, another switch. Many “dead NAS” cases are dead switches.
Several disks showing alerts, or unreadable files: stop all writes, do not rebuild blindly.
Volume still readable: copy the critical folders off the NAS first, repair afterwards.
Internal snapshots die with the NAS: only the external copy counts.
The NAS is a source to be backed up, not a backup.

1. Find out how far the problem goes

Symptom	Likely cause	First step
Only one workstation can no longer see it	The workstation: network drive, password, VPN	Test from another workstation
No workstation can see it, nor the admin interface	Network, power supply or device frozen	Ping, status lights, another cable, another switch
The interface reports a failed disk	Degraded volume, still healthy if the RAID has some margin	Replace the disk indicated by the manufacturer, not another one
Several disks showing alerts, volume degraded beyond the RAID, unreadable files	Loss of redundancy or corruption	Stop all writes, do not rebuild blindly
Files renamed or encrypted en masse	Attack	Disconnect the NAS from the network and follow the ransomware guide

Many “dead NAS” cases are dead switches.

If the files on the NAS have changed extension or display a ransom demand, this is not a failure: disconnect it from the network without shutting it down and go to Ransomware has just struck.

2. Protect what is still responding

If the volume is still readable, immediately copy the most critical folders to a disk that is not in this NAS, in addition to the backup already held off-site. Then run the repair recommended by the NAS manufacturer.

A RAID rebuild puts heavy load on all the remaining disks. On a second failing disk, it can destroy the volume: if two disks are suspect and an external backup is good, restoring from the external copy is often safer than rebuilding.

3. Restore from the copy outside the NAS

If the volume is dead:

restore the shares from the off-site backup to a new volume, another NAS or a server;
reapply the permissions, or recover them if the NAS configuration was itself backed up;
recreate the tasks and accounts. Without a configuration export, this part has to be redone by hand: it often takes longer than copying the files.

Snapshots internal to the lost NAS are no longer available. NIST puts it this way in its storage security guidelines: if the source data is unavailable, the snapshots can no longer be used either. Only the copy that left the device is of any use.

RAID, snapshots, external backup: what protects against what

Risk	RAID	Internal snapshots	Backup outside the NAS
Single disk failure	Yes	No	Yes
File deleted by mistake	No	Yes, as long as the NAS is working	Yes
Failure of the NAS itself	No	No	Yes
Ransomware with administrator access	No	Often not	Yes, if the copy is isolated or immutable
Fire, theft, water damage	No	No	Yes, if it is on another site

CERT-MU, in its guideline on backup plans, recommends keeping an off-site copy and regularly testing restoration. The French cybersecurity agency (ANSSI) recommends the “3-2-1” rule: three separate copies of the data, two backups on different media, one of them offline.

4. Afterwards

Put an external backup back in place on the day the NAS returns to service. Check the overnight alert. If the NAS was the only copy of the workstations’ data (“we save to the NAS, so it’s backed up”), the scope was wrong: the NAS is a source, not a backup. See How do you back up a NAS? and Why make an off-site backup?.

At WeDoBack

NAS devices are among the sources WeDoBack includes in its off-site backup: data is encrypted on the machine before it is sent, with a key held by the customer, then stored on servers dedicated to backup, separate from production. Restoration covers the copied data, to a healthy location, not the repair of the RAID. If the NAS hosted the company’s only file server and downtime is intolerable, the critical content should live on a server covered by a DRP, not only on a NAS restored file by file. Support can be reached on +33 9 72 50 78 28, from 9:00 to 13:00 and from 14:00 to 17:30 (Paris time), i.e. from 11:00 to 15:00 and from 16:00 to 19:30 Mauritius time during European summer time, and one hour later in winter.

Call +33 9 72 50 78 28 Request a quote

Frequently asked questions

Isn’t RAID enough to protect the data on the NAS?

No. RAID lets you survive the failure of one disk, sometimes two. It does not protect against deletion, ransomware, controller failure, fire or theft: all the copies are in the same box. ANSSI, France’s cybersecurity agency, recommends three copies, on two different media, one of them offline.

Are NAS snapshots a backup?

They let you quickly go back to a previous version of a file, as long as the NAS is working. NIST points out that if the source data becomes unavailable, the snapshots can no longer be used either. They complement an external backup; they do not replace it.

Should the disks be sent to a data recovery specialist?

Only if no clean external copy exists and the data is valuable. In that case, shut the NAS down properly, number the disks in their original order and do not attempt anything. Every rebuild attempt reduces the chances of recovery.

Sources

Documents consulted in October 2026.

Information system backup – The fundamentals (ANSSI-BP-100, v1.1, 27 November 2025, in French) — ANSSI (French cybersecurity agency)
SP 800-209, Security Guidelines for Storage Infrastructure (October 2020) — NIST
Guideline on devising a personal backup plan (CMSGu2017-03) — CERT-MU
Guideline on Ransomware Removal — CERT-MU
DRP offer (Disaster Recovery Plan) — WeDoBack

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