Two discs that wore out together. A resync that copied the wrong way round. A box that failed with both members in perfect health inside it. None of those is a dead end. Each half is imaged on its own, the two are judged on what they actually hold rather than on a status flag, and your files come off whichever proves the stronger.
A mirror is quoted, never guessed at. Diagnosis costs nothing and the written figure comes after it — from £500 + VAT counted by disc, with logical work under no fix, no fee.
A mirror makes one promise and keeps it well: the volume carries on when a single disc dies. Every position below goes around that promise rather than through it, which is why they end up in a padded box on the way to Guildford.
Two drives from one order, powered up on the same morning and given identical work ever since, do not politely fail years apart. The gap is usually weeks, and whatever wore the first one out has been doing the same to its partner throughout.
In a two-bay NAS or a mirrored desktop, the first thing to fail is generally the controller or the bridge rather than a member. Two perfectly sound discs end up sealed inside a case that no longer speaks to anything, and each then has to be read on its own terms.
Reinsert the wrong disc, or leave the enclosure to work it out unsupervised, and the empty or out-of-date member is copied straight over the current one. The mirror does exactly what mirrors do, at full speed, in the wrong direction.
Where the pair ran degraded at different times, each ends up holding a different version of the same folders. Merge them carelessly and they spoil each other. Copy them apart and each is free to give up whatever only it still holds.
A deletion, a corrupt write, a bad update, an encryption run: mirroring exists to reproduce writes the instant they happen, so all of those reach both halves together and neither disc is spared any of it.
A NAS firmware update that fails partway, or an operating system that eats its own boot volume, leaves a dead box with two healthy discs locked inside. The way out is to copy each disc and raise the volume on hardware that works.
Consider what mirroring actually promises. Two discs are kept byte for byte identical, in real time, by copying each write to both of them before the operating system is told the write finished. Nothing in that arrangement inspects the write or has an opinion about it. Emptying a folder is a write. Encrypting a file is a write. Saving a mangled version over a good one is a write. Every one of those instructions is carried out faithfully on both members at the same instant, which is precisely what a mirror is for and precisely why it protects you from so little.
Set the two ideas side by side and the confusion clears. A backup is a copy of how things stood at some point in the past, kept apart from the original. A mirror is a live duplicate kept in the same chassis, on the same power supply, behind the same controller. One lets you return to Tuesday. The other lets you keep trading through a dead disc, which is worth having and is not the same service. Neither a deletion, nor a corrupt update, nor an encryption run, nor a lightning strike on the mains is answered by the second. Worth adding: nothing on this site is a backup product. There are no contracts and nothing to subscribe to. This is a bench that gets data back, and it will happily tell you where the copies ought to have been living instead.
Every member carries a short status record — a counter that ticks with each event, a timestamp, a flag for whether that disc is currently in step. On assembly the two records are compared and the higher counter is treated as authoritative. That design works, and it accounts for most resync accidents. Take a disc out for a fortnight and return it, and its counter is genuinely behind, so the enclosure overwrites it, which is the right decision. But bring a mirror back up after the controller has failed and those records may be absent, damaged or misread, and the same logic reaches the wrong conclusion with identical confidence.
Nothing in the recovery depends on that record. Both members are copied first, and the better source is chosen on the contents rather than the flag: which image carries a coherent file system, which holds the later versions of documents whose dates you recognise, which shows the tell-tale pattern of having been written over. Reading a counter takes a second and can be wrong; reading the discs takes longer and is very much harder to mislead.
Nearly every pair that arrives came out of a two-bay Synology, QNAP or Netgear box, or a small server under a desk: architects and surveyors around Wokingham and Windsor, letting agents and practices in Maidenhead and Ascot, engineering firms towards Camberley and Sandhurst, studios and agencies posting in from the London districts. Put both discs in one parcel to Guildford Data Recovery, Building 2, Ground Floor, Guildford Business Park, Guildford GU2 8XH, tracked and insured. The wider picture is on RAID recovery and NAS recovery, the whole county is covered from data recovery Berkshire, and every band is published under data recovery cost.
A mirror can serve a read from either disc, which sounds harmless and hides a slow problem. Sectors go soft gradually. An enclosure with no scrubbing routine has no reason to touch a rarely used region for months, so a member can be quietly rotting while the volume reports itself healthy. When symptoms finally surface they are peculiar rather than dramatic: a document that opens on Monday and refuses on Thursday, a check that passes and then does not, software complaining about data it wrote itself. If that is the pattern that brought you to this page, both discs matter more than usual — the intact version of any given file may survive on only one of them.
The pair is separated the moment the box is opened and treated as two independent recoveries. Each member goes onto a hardware imager, and any disc with a physical fault is stabilised at the clean bench before that starts. Then the two copies are set against each other: which contains more of your material, and which contains the newer version of it. Whichever wins becomes the base for the rebuild and the other fills its gaps. At no stage is anything written to either original.
Synology lays its own volume manager over the standard Linux arrangement and a modern file system over that; QNAP does something similar with different names; X-RAID on a Netgear box adds expansion logic all its own. All of them can be read, and none of them can be read by pushing a member into a Windows machine and hoping. The practical consequence for you is small: send both discs rather than one, note which bay each came from, and say what make and model the unit was.
The first is to stop as soon as you notice. A backwards resync takes a little more with every write it completes, so the minute between noticing and pulling the plug is genuinely the most valuable minute in the job. The second is to leave the discs alone. Trying each member in turn in a desktop machine to see which one works achieves nothing useful: at best you learn something the images would have told you anyway, at worst Windows offers to initialise the disc and somebody accepts. Initialise is the one word on this page that turns a routine job into an awkward one.
Both halves copied apart, the better one raised, the weaker one filling the gaps. Diagnosis is free.
Hardly anything walks into this lab; it arrives in a padded box. Tracked, insured post is the least stressful thing that can happen to storage that has already given up, and a parcel handed over at a Bracknell post office before the last collection is usually in Guildford the following working day.
Is the storage still bolted into a machine — laptop, tower, iMac, MacBook, rack server, a DVR under the till? Free it first and send the bare unit. Stripping hardware is not something this lab does, though it is ten minutes' work for any repair shop on your high street. There is a single case with no way round it: memory chips soldered flat onto the mainboard, which is how Apple Silicon machines and certain ultrabooks are built. Where the storage cannot be unbolted, there is no parcel to make up.
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The name on the parcel wants to be Guildford Data Recovery. Driving it over from Bracknell is roughly forty minutes on the A322 then the A3; posting it costs you a stamp and a day. Either way, a message goes out to you as soon as it is logged onto the system, and two working days later the diagnostic is finished.
Unsure whether something should go in the box? Ring 0800 689 0668 while the lid is still open, or work through the free online diagnostic and let it tell you.