An eight-disk array lost a second member during a rebuild and a third while the business tried to keep trading on it. By the time it reached us the volume was gone and the remaining disks had been running hard for four days.
A manufacturing business ran its production and design files on an eight-disk RAID 6. One disk had failed months earlier and been left; a second failed during the replacement rebuild, and the array degraded to its limit. Rather than stopping, the rebuild was restarted twice more while staff continued working from the volume — and a third member dropped out on the second attempt.
RAID 6 carries two parity blocks per stripe and genuinely survives two failures. Three is beyond the design, but not automatically beyond recovery: the question is whether the third disk failed completely or simply dropped out. Here the third was electrically sound with a large but bounded band of bad sectors, and the second was mechanically failing. Only the first was truly gone.
All eight members were imaged read-only, worst-condition first — the disks least likely to survive were read while they still responded, rather than being left until last. The mechanically failing member needed a donor head-stack before it would image at all. Unreadable sectors were logged rather than guessed at, so the map of gaps was known precisely.
The array geometry was then derived from the images and the RAID 6 assembled virtually. With six clean members plus substantial coverage from the seventh and eighth, dual parity reconstructed the overwhelming majority of stripes — only those with three unreadable members in the same place could not be resolved.
CAD files were opened in their application, production databases checked for structural consistency rather than merely copied, and the folder structure matched against what the business expected. The small number of unresolved files were reported by name.
Around 99% recovered. Worth noting what actually caused the loss: not the first failure, which RAID 6 absorbed easily, but four days of continued use and three rebuild attempts on a degraded array. Had it been powered down when the second disk dropped, this would have been a straightforward job.
A rebuild reads every sector of every surviving member — hours of maximum stress on disks the same age as the ones that just failed. Repeating it on an already-degraded array is how a recoverable set becomes a marginal one. When an array passes its redundancy limit, power it down and preserve bay order. Emergency RAID work starts from £500 +VAT.
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Often, yes. Three failures exceed the design but not necessarily the recovery — what matters is whether the third disk failed completely or merely dropped out. A member with bad sectors still contributes most of its data, and dual parity fills a great deal of the rest.
No. Each attempt reads every sector of every survivor, and on disks the same age as the ones that already failed, that is the operation most likely to cost you another member. Power the array down instead.
It is the most expensive decision available. A degraded array has no margin left, and continued use is the commonest reason a recoverable set becomes a partial one. Stop, secure the data, then rebuild.
From £500 plus VAT, quoted in writing after a free 48-hour diagnostic, with priority handling available. Physical drive work carries a 50% deposit and the balance is due only on success.
Start with an instant online quote, or call and talk it through with us first. You'll have a clear, fixed price before any work begins.