Data Recovery Case File · NAS & Network Storage · It Told You Which One
An Indicator Per Member Reports Which Disk the Appliance Has Stopped Trusting
His enquiry reports a state rather than a symptom, and the state is specific. A two-drive mirrored storage box with three indicators — power, disc one and disc two — where "power and disc two are blue as normal but disc one is red, indicating a failure." That is considerably more information than most enquiries carry: the appliance has not merely stopped, it has identified which of its two members it considers to have failed.
| Media | Two-drive mirrored storage appliance — power and second-member indicators normal; first-member indicator in a fault state |
| Reported situation | Two-drive mirrored storage appliance in use · three status indicators present for power and each member · power indicator normal · second member indicator normal · first member indicator in a fault state · appliance still powered · repair or recovery options queried |
| Fault class | Single member reported failed within a mirror — remaining member holding a complete copy; rebuild activity presenting the principal risk to it |
| Equipment used | Per-member indication treated as identifying the affected disk rather than as general failure · appliance powered down before any rebuild could be initiated · both members imaged individually write-blocked before any interpretation · the healthy member assessed first and read in full · the reported-failed member assessed independently to establish genuine condition |
The decode: what the pattern establishes, and the one thing to avoid
Why per-member indicators are worth more than a single status light: they localise. An appliance with a light for each disk reports its assessment of each disk separately, which is a conclusion it has already reached and displayed.
What the normal indicator on the second member establishes: that one is fine. The appliance is reading it, considers it healthy, and by the design of a mirror it holds a complete copy of everything.
Why that is the whole of the good news: nothing is lost. A mirror exists precisely so that one member can fail without consequence.
What the fault indicator on the first member does and does not mean: the appliance stopped trusting it. That covers a genuinely dead disk, a disk returning errors, and a disk the controller could not reconcile after an interruption.
Why the distinction matters less than it might: the other member is complete. The condition of the failed one affects whether it can contribute, not whether the data survives.
Now the action to avoid, and it is what the appliance will invite: replacing the member and rebuilding. A rebuild reads the surviving member end to end under sustained load to copy it onto a new disk.
Why that is the moment of maximum danger: the good member is asked to do the most demanding thing it does, alone. Mirrored disks are usually the same age and have had the same use, so the survivor is often not far behind the one that failed.
Why the appliance still being powered is itself a concern: rebuilds start automatically. Some units begin recovering onto a replacement, or onto a spare, without being asked.
What should happen first: the surviving member copied while it is healthy. Imaging it produces a complete copy before any rebuild is attempted, after which a rebuild costs nothing if it fails.
Why the failed member is still assessed: it may be fine. A disk marked failed after an interruption frequently reads normally on other equipment, and two copies are better than one.
On the bench
Per-member indication was treated as identifying the affected disk rather than as general failure — an appliance with an indicator per disk displaying an assessment it has already reached for each, so a normal second indicator establishes that member as readable and, by the design of a mirror, complete. The appliance was powered down before any rebuild could be initiated, a rebuild reading the surviving member end to end under sustained load when it is usually of the same age and use as the failed one.
The outcome
Per-member indication read as identifying the affected disk, the appliance powered down before any rebuild, and the healthy member imaged first. Free assessment, one fixed written figure including VAT, charged per drive, with 50% of parts and labour upfront where a drive has to be opened. The decode: your box has already told you which disk it stopped trusting, and that the other one is fine. A mirror means that other one holds everything — which is exactly why it should be copied before anything is rebuilt.
One disk flagged in a two-disk mirror
Power the appliance down rather than replacing the flagged disk — some units begin rebuilding automatically, and a rebuild asks the surviving member to be read end to end under sustained load, alone. Mirrored disks are usually the same age with the same use, so the survivor is often not far behind the one that failed. Read the indicators as good news first: a normal light on the other member means the appliance considers it healthy, and a mirror means it holds everything.
Power it down — call Cambridge Data Recovery on 01223 655015; per-member indication read as identifying the disk, healthy member imaged before any rebuild, flagged member assessed independently.
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Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.