Data Recovery · LanCologne

What technical considerations are there to bear in mind when recovering data from a Synology NAS with an SHR array?

Synology Hybrid RAID (SHR) divides hard drives of different sizes into several partitions and uses these to form several Linux RAID arrays (mdadm), which are then combined into a single volume via LVM. Btrfs or ext4 is mounted on this volume. A recovery operation must reassemble these segments in the correct configuration.

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Technical background

Typical failures: a second disk failure during repair, „Volume crashed“ following a power cut, failed DSM-Updates. With Btrfs, checksums and snapshots are also used; this helps to detect corrupted data, but makes repair more challenging.

What you should – and shouldn’t – do now

  • Do not initiate a „repair“ or a rebuild of the storage pool.
  • Do not insert the panels in a different order.
  • Do not connect any drives to Windows PCs that prompt you to initialise them.
  • If encryption is used: have the key file or password to hand.

Here’s how we do it

  • Raw images of all the plates.
  • Analysis of the partitions and mdadm superblocks for each segment.
  • Reconstruction of the LVM and mounting of Btrfs or ext4 on the image.
  • With Btrfs: selection of a consistent older version of the metadata if the current one is corrupted.

Borders

  • Encrypted shared files cannot be read without a key.
  • If the redundancy of a segment is exceeded and a disk cannot be read, data from that segment is missing.

Possible results

Restored access permissions and a statement regarding the areas affected.

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

How does SHR differ from standard RAID?+
SHR consists of several RAID arrays spread across partitions on different disks. This makes reconstruction more complex.
Does Btrfs help with data recovery?+
Yes and no: Checksums indicate corrupted data, and older versions of the metadata can be helpful. However, repair commands applied to the original file may cause damage.
Can I replace a disc if DSM offers this option?+
If only one disc is affected and there is a recent backup, then yes. If the volume has already „crashed“, you should back it up first.

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