I asked Seagate to show what my own RAID recovery looked like, and this was the result.
“I know you want eye candy,” says Peter Oswald, “but most of what we do is going to look really normal and ordinary to people who don’t know what we’re doing. This controller you see here looks like a plain card, but it was designed specifically for us, just like the software. It’s controlling the power…just many, many components of these drives. It’s controlling very small details that go on in the background.”
In my case, my drives weren’t responding in a timely manner to the NAS system’s requests, and so the request would time out. But whatever in the NAS “environment” was causing that issue was likely also impacting the other drives. So eventually, the enclosure system tagged one drive as bad, continued to operate in degraded RAID 5, and when the second drive failed, the RAID collapsed. Seagate had to construct a new environment for the four drives in which the drives were instructed to believe they were healthy. With this done, technicians could begin copying my data out to other storage. Interestingly, this doesn’t mean that the RAID was back in working order. The highest priority was simply to extract my bits from the drives and copy them in a “de-striped” state onto known good media. Then the recovery crew could begin trying to piece together my file structures and reconstruct the original four-disk volume’s architecture.
All told, Seagate spent roughly 28 man-hours recovering my data. Much of this involved identifying the critical data structures across all four drives, determining the correct stripe sizes, and finding out the ages of the data to see which came before and after the loss of the first drive.