Data Recovery · LanCologne

What should be borne in mind when carrying out data recovery from a RAID-10 array with several failed hard drives?

RAID 10 consists of mirrored pairs across which the data is distributed in stripes. If two discs fail, the allocation determines the outcome: if they belong to different pairs, all the data is still intact. If an entire pair fails, stripes are missing – in which case the only solution is to restore the faulty disks to a readable state yourself.

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Technical background

It is not always obvious how the drives are assigned to the pairs, particularly in NAS systems (e.g. Linux RAID „near“/„far“ layouts) or following drive replacements. Often, one of the failed drives is still partially readable; even just a few additional readable sectors can be enough to reconstruct many files.

What you should – and shouldn’t – do now

  • Do not start a rebuild onto a spare disk until it is clear which pairs are affected.
  • Keep any spare plates and label them.
  • No reinitialisation.

Here’s how we do it

  • Images of all discs; faulty discs with hardware for unstable drives.
  • Determining pair assignments, stripe size and layout.
  • A composite made up of the best copies from each pair; missing areas are marked.

Borders

  • If both discs in a pair are unreadable at the same point, that data is lost permanently.
  • Databases and large files are more severely affected by security vulnerabilities than many small files.

Possible results

Recovered volume containing a list of complete and incomplete files.

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 many drives can a RAID 10 array lose?+
At least one; more only if no pair of mirrors fails completely.
How do I know which records go together?+
From the controller configuration or by analysing the data on the discs.
Is it worth repairing a faulty hard drive?+
Often, yes – especially if their partner is also faulty.

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