Well at least on Linux, by default almost everyone (using consumer drives) has their array in a very common misconfiguration. And this leads to raid5 collapse much sooner than it should.<p>The misconfiguration is the drive&#x27;s SCT ERC timeout is greater than the kernel&#x27;s SCSI command timer. So what happens on a URE is, the drive does &quot;deep recovery&quot; if it&#x27;s a consumer drive, and keeps trying to recover that bad sector well beyond the default command timer of the kernel, which is 30 seconds. At 30 seconds the kernel assumes something&#x27;s wrong and does a link reset. On SATA drives this obliterates the command queue and any other state in the drive. The drive doesn&#x27;t report a read error, doesn&#x27;t report what sector had the problem, and so RAID can&#x27;t do its job and fix the problem by reconstructing the missing data from parity and writing the data back to that bad sector.<p>So it&#x27;s inevitable these bad sectors pop up here and there, and then if there&#x27;s a single drive failure, in effect you get one or more full stripes with two or more missing strips, and now those whole stripes are lost just as if it were a 2-disk failure. It is possible to recover from this but it&#x27;s really tedious and as far as I know there are no user space tools to make such recovery easy.<p>I wouldn&#x27;t be surprised if lots of NAS&#x27;s using Linux were configured this way, and the user didn&#x27;t use recommended drives because, FU vendor those drives are expensive, etc.