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RDR / What we take in / RAID 1 mirrors

Specialist · RAID 1 mirrors

RAID 1 data recovery, Reading. A mirror fails quietly: both sides can be wrong for months before it says so.

RAID and NAS work starts at £500 + VAT and the diagnosis before it is free. A mirror writes everything twice, so either disk ought to carry the whole volume — which is why the failures that actually arrive here are not the one people expect. Two disks bought together wear out together. A tired controller writes the same corruption to both sides at once. A rebuild copies the failing member across the sound one. And a mirror that dropped a member last spring has run on ever since with nothing behind it. Each member is cloned read-only and on its own, the two copies are compared block by block, and the volume is assembled from whichever side reads and whichever side is the newer. Sets reach the bench by post from Reading, Theale, Woodley, Earley, Newbury, Didcot and Basingstoke, and your own disks go home unwritten to.

Nothing recovered? On most jobs, nothing to pay The diagnosis is free; then one fixed figure in writing Parcels arrive from Newbury, Woodley and Theale

An engineer answers, and looking is free
0800 6890668

Match the symptom to the fault.

Different fault? Begin at the triage →
What you are seeingWhat is likely wrongWhat happens next
The box reports the volume as degradedA member has left the mirror, and the other disk is carrying it with nothing behind itCopy off what you can, then send both
Both disks are the same age and both are slowingMirrored members do identical hours, so they tend to wear out togetherTake the box off power now
A new disk went in and the good copy went blankThe set re-synced the wrong way and wrote the failing member across the sound oneStop there, and send both disks
Files are missing from both members at onceA mirror copies a bad write to both sides as it happensDo not let it re-sync
The amber light has been on since the springThe mirror has run on one disk for months with no second copy behind itSend both, not only the failed one
Windows shows the mirror as Failed RedundancyA member has been dropped from the set. The disks themselves are often soundDo not re-enable it or import it
Packing and posting: pad it so nothing can move, put a cover value on the parcel that reflects what the files are worth to you, and send it tracked to the intake lab. Return postage is ours. Ring first if you would rather an engineer talked the packing through before the box is sealed. It is all set out on the packing and postage page.

What a RAID 1 mirror protects you from, and what it does not.

Two-bay boxes set to mirrorA Synology, QNAP or desktop enclosure holding two disks, with the safer of the two settings chosen at setup. Linux software RAID underneath means the description of the mirror rides on the members themselves, so the chassis can stay on your desk — though a network box may be sent whole if you would rather not open it.
Boot pairs and RAID cardsThe pair of disks a small server starts from, mirrored on a hardware controller or through Intel RST on the motherboard. The card writes its own account of the set onto both members, and that can be read from images without the original card and without the original machine.
Windows, mdadm and ZFS mirrorsA mirrored dynamic volume or Storage Spaces under Windows, an mdadm pair under Linux, a two-disk ZFS or btrfs mirror on a NAS. Each keeps its layout on the disks, each can be assembled over copies, and each has its own way of deciding which member it trusts — which is precisely the question when they go wrong.
Why a rebuild can make it worseOn RAID 5 or 6 a rebuild works the absent disk out from parity. On a mirror there is nothing to work out: it copies one member straight over the other, in whichever direction the controller has settled on. Where that direction is wrong, the only good copy goes in an afternoon. Recovery here happens on images instead, where a wrong turn costs nothing but time.

From your parcel to your files coming back.

Jobs we have closed →
01

Logged the day it lands, and the look costs nothing Free

A case number goes on your device the day it reaches us, and an engineer then finds the real fault — free, and before anything else happens. You are told plainly what will come back and what will not, with one fixed figure in writing beside it. Nothing chargeable starts until you have read that and said yes.

The look costs you nothingA fixed price, in writingStill nothing to pay
02

Both members copied on their own

Each disk goes behind a write blocker and is cloned end to end before a single file is opened — the sound member as carefully as the one that stopped, because on a mirror the sound member is half the answer. Weak ground gets brief runs and waits its turn until last. Not a byte returns to what you sent in.

Nothing is written to your disksOne member at a time
03

The two copies compared

A mirror gives you two versions of the same volume, and the work is deciding which to believe. The set's own metadata records when each member last took a write; the file systems on the images supply the rest. Where the two disagree, the readable and the newer copy wins, block by block, and the reasoning is written down rather than assumed.

Which side is newer, provedCompared, never assumed
04

The volume built from the better copy

With the two sides settled, the volume is stacked back over those images and the file system put right on the copy. Then the files get opened rather than tallied — accounts, shared folders, databases, photographs — because a name in a listing proves nothing whatever. Whatever returns damaged is written down as damaged.

Each file opened, not countedDamaged ones named as damaged
05

The list first, then the bill, then the files

You see the file list first, then decide. Nothing is invoiced until you have said yes, and on most jobs there is no fee at all if the data does not come back. What we pull off goes onto media bought in for your job, and the postage home is ours. The case stays open on the bench until you tell us the files open on your own machine.

Nothing billed until you say yesNew media, bought for the jobPostage home is on us

What goes wrong most often

  • A mirror is not a backup and was never sold as one — it copies every write to both disks as it happens, so a deletion, a corrupt write or a ransomware incident lands on both sides at the same moment. What it protects against is one disk failing. That is worth having, and it is the whole of what it does.
  • Two disks bought together fail together — same batch, same shelf, same hours, same heat. The second member very often begins to go within weeks of the first, which makes a degraded mirror a far shorter grace period than people expect, and means the disk still sitting in the bay is not automatically the good one.
  • The direction of a re-sync is everything — it writes one member across the other, and a controller decides which way round on its own logic. Copying a failing disk over a sound one, or a stale member over a newer one, is how most of the bad cases here began. If a box has offered to rebuild, decline it and ring before anything else happens.
  • Send the disk the box wrote off — the member that dropped out is frequently the one holding the newer data, and it is nearly always readable enough to be worth imaging. Sending one disk and keeping the other halves what can be done, and now and then rules the job out altogether.

Where the honesty has to come in: storage is the whole of what this bench handles. Mirrors are what this page covers — two disks in a network box or a desktop enclosure, a pair on a RAID card or a motherboard controller, a Windows mirrored volume, an mdadm or ZFS mirror — and they arrive failed, degraded, re-synced the wrong way or written over. Where both sides can be read, the volume goes back together over the copies and the folders come home in the arrangement you had them in. What nobody can do is produce blocks missing from both members: where the same ground has failed on each side, some files return with holes, and the report names them. Nothing withstands being written over either. Encryption needs its key from you. We take no phones and no tablets. This work is from £500 + VAT, quoted in writing after a free look, and where nothing is recovered, most jobs are not charged for.

How one of these actually went.

RG · RDG-2026-1996ON FILE ✓

A mirror that had been running on one disk since the spring

A distributor off the Theale estate rang when the accounts server would no longer mount its data volume. The mirror had dropped a member months earlier — the amber light was on a chassis behind a door nobody opens — and the disk still working had been carrying the lot on its own ever since, and had begun to fail in turn. Both went on the imager separately, the worn one in short passes across two nights. Where a block would not read on the tired disk it was taken from the older member instead, and where the older member was out of date the newer copy won. The stock database and eleven years of delivery notes were opened on the bench before anything travelled back. Three days, parcel to parcel.

Each of themembers imaged one at a time3 days from arrival to return

What helps, and what makes it worse.

First things to do

  • Take the power off the box and leave it off
  • Send every member, the failed one included
  • Write the bay number on each disk before it comes out
  • Say whether a rebuild or re-sync has been started

What makes it worse

  • Letting the box re-sync onto a fresh disk
  • Reactivating a mirror Windows has marked Failed
  • Running repair tools against either member
  • Sending one disk and keeping the other

Answers before you commit to anything.

One disk still works. Why do you want both of them?

Because a mirror hands you two versions of one volume, and by the time it fails they are rarely identical. One side may hold blocks the other can no longer read; the other may be weeks out of date because it left the set long before anybody noticed. With both images on the bench, each block is taken from whichever side reads and whichever side is the newer — an advantage a striped set never offers. Send both, with the bay each sat in written on it, and include the one the box has written off.

The box is offering to rebuild onto a new disk. Should I let it?

No, and this is the mistake that costs people most. A rebuild copies one member straight over the other, and the direction is chosen by the controller rather than by you. Where the disk left in the bay is the failing one, or the stale one, the rebuild writes it across the good copy and there is no second version left to work from. Take the power off the box, leave the disks where they are, and let images be taken first. Once copies exist, nothing pressed afterwards can undo them.

I deleted a folder and it went from both disks at once. Is a mirror not a backup?

It is not, and that is what a mirror is most often bought for by mistake. Mirroring copies every write to both members as it happens, so a deletion, a corrupt write or a ransomware incident reaches both sides at the same moment. What a mirror protects you against is one disk failing, and nothing else. What can be recovered afterwards is whatever has not since been written over, which is why the box wants taking off power the same day rather than the same week.

What do I send, and what does it cost?

RAID and NAS work starts at £500 + VAT, the look before it is free, and one fixed figure reaches you in writing before anything chargeable begins. Send every member of the set with its bay number written on it, the one marked failed included, and say what has already been tried. A network box may be sent whole if you would rather not open it; disks out of a server or a desktop enclosure come bare, in antistatic bags. There is no collection and no counter, so it travels tracked and insured to the intake-lab address on the contact page.

If this sounds like yours, start here.

Servers that will not boot → Fujitsu laptops → Servers and RAID arrays → Every device we handle →

Nothing gets worse while it sits switched off.

You pay nothing for the look. What comes back is a list — the files that opened, the ones that did not, and one fixed figure to finish the job. Leave it switched off until you have that in writing.

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