| FYI
I dropped the array, and created a Raid 6 using all 5 drives (Raid 10 only uses 4).
It seems I couldn't make Raid 5 use the 5th disk because it was faulty. The array now seems permanently downgraded until I can get another drive in it.
When I tried Raid 6 it configured but then immediately went into degraded mode. I'm in the process of replacing the new (faulty) disk with a new (good) disk. |