Data Recovery · LanCologne

What should you bear in mind when recovering data from a QNAP NAS system?

If a QNAP NAS fails, the data is usually still stored on the hard drives – but in several layers: Linux software RAID (mdadm), overlaid by the Logical Volume Manager (LVM), and in some newer models thin provisioning and snapshots, with an ext4 file system typically running on top of this under QTS and a ZFS file system under QuTS hero. Data recovery is only possible if each of these layers is reconstructed in the correct order.

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Technical background

Typical causes include a second drive failure during a rebuild, a failed Update firmware update, an accidental reinitialisation, or a static volume/storage pool error following a power cut. The message „Storage pool unavailable“ does not automatically mean that the data has been lost; often, it is simply that the RAID or LVM metadata is inconsistent.

What you should – and shouldn’t – do now

  • Before initialising or „repairing“ the storage pool, ensure that all disks have been backed up or checked first – both operations may overwrite RAID and LVM metadata.
  • Do not insert the discs in a different order; do not confirm any Windows prompts to initialise or format individual discs.
  • Make a note of the slot allocation (Slot 1, 2, …) or label the boards.
  • If encryption is used: Have your password or exported key file to hand.

Here’s how we do it

  • Back up each disk individually as a read-only raw image; start with the unstable drives.
  • Analysing mdadm superblocks: RAID level, order, chunk size, event counter.
  • Reconstruct the LVM or thin pool metadata and reassemble the volume virtually.
  • Check the file system (ext4 or ZFS) on the image and extract the data – do not do this on the original discs.

Borders

  • With QTS volume encryption, decryption is not possible without a password or key.
  • If a rebuild was started with the wrong drive order following the failure, some sectors may have been overwritten.
  • Thin provisioning and snapshots significantly increase the effort involved in reconstruction.

Possible results

The result is a list showing which volumes and shares could be reconstructed, and which files are fully or only partially readable.

How we carry out data recovery

Every data storage device is first diagnosed in our own laboratory in Cologne; the diagnosis is free of charge. You will then receive a written quote and can decide whether to accept it. If you decline, you can collect the data storage device from the laboratory by appointment – there are no postage costs involved – or we will post it back to you; in which case postage and packaging costs may apply. Data is recovered from copies, not from the original – using professional data recovery hardware such as the PC-3000. If a drive needs to be opened, this is carried out on a HEPA H14-filtered clean bench. We do not offer a guarantee of success prior to diagnosis, as this is simply not possible in a professional context. Your storage device and your data will remain confidential and will not be passed on to third parties.

1Enquiries and submission by post or in person at the laboratory by prior appointment
2Free diagnosis of the cause of the damage
3Written quotation – we will only proceed once you have approved it; if you decline, you may collect the item from the laboratory or we will return it to you (postage and packaging costs may apply)
4Recovery, data verification and confidential handover

Request a diagnosis   Find out more about the process, costs and confidentiality →

Frequently Asked Questions

Can I simply transfer the hard drives from the QNAP into a new QNAP?+
Only after the discs have been backed up or checked. A new device may recognise the discs as „new“ and offer to initialise them, which will overwrite the metadata.
What information would be helpful in making an assessment?+
Model, number and configuration of the drives, RAID level (if known), operating system (QTS or QuTS hero) and whether encryption was enabled.
How many discs can fail before it’s still possible to salvage anything?+
That depends on the RAID level and on whether the failed drives are still partially readable. Even if the redundancy threshold has been exceeded, partial data recovery is possible if the faulty drives can still be read.
Does it matter whether QTS or QuTS hero was used?+
Yes. QTS generally uses mdadm, LVM and ext4, whereas QuTS hero uses ZFS (pools, RAID-Z, snapshots). The reconstruction process differs fundamentally; with ZFS, too, the work is carried out logically using images. It is not possible to guarantee success before a diagnosis has been made.

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