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Are you using Raid6 for both data and metadata? If yes, you could just as well have been running raid 0 and having more space and performance out of the same disks. Because of well documented issues, metadata on raid6 is not yet safe in power/hw failure situations. And if you have no safety in those situations, what is raid even for?

(It's perfectly safe to run metadata on raid1 and data on raid5/6.)

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I'm running RAID6 for data and RAID1 for metadata. Wanted the metadata replicated. So far I've had no HW failure situations and I have suffered a few power outages while I was away from home even though I have a backup battery.

Although these drives have surpassed 50,000 hours of running time, I am fairly certain the day of reckoning is coming, but I have backups and a plan to recover.

I may recover to something not BTRFS. Not sure just yet.

With data on raid6 you should be running metadata on raid1c3 or raid1c4, not raid1 nor raid5/6.

Wait, what's wrong with metadata on raid1?

Metadata on raid1 doesn't guarantee the resilience to two-drive failures that raid6 is used for, but metadata on raid1c3 does give you that degree of resilience (with more space overhead, but that's seldom a problem for the metadata).

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