The Mechanism
Hardware RAID controllers communicate with drives using strict timing thresholds. Enterprise drives feature technologies like TLER (Time-Limited Error Recovery), which ensure that if a drive hits a bad sector, it stops trying to fix it after a few seconds and lets the RAID controller handle it.
The Impact on RAID 6
If a system builder mistakenly uses consumer-grade desktop or external drives in a large RAID 6 array, those drives lack TLER. When a consumer drive hits a stubborn bad sector, it may freeze for up to a minute trying to self-repair. The enterprise RAID controller assumes the drive has completely died and forcibly drops it from the array.
In large enclosures (e.g., 12 to 24 bays) running high-vibration consumer disks, it is highly common for three or more drives to experience these timeout delays simultaneously under a heavy workload. The controller will drop all of them, killing a healthy array purely due to software timeouts.
