I lost enough Btrfs m=d=s=RAID5 filesystems in past experiments (I didn't try using RAID5 for metadata and system chunks in the last few years) to faulty SATA cables + hotplug enabled SATA controllers (where a disk could disappear and reappear "as the wind blew"). Since then, I made a habit of always disabling hotplug for all SATA disks involved with Btrfs, even those with m=d=s=single profile (and I never desired to built multi-devices filesystems from USB attached disks anyway but this is good reason for me to explicitly avoid that). I am not sure if other RAID profiles are affected in a similar way or it's just RAID56. (Well, I mean RAID0 is obviously toast and RAID1/10 will obviously get degraded but I am not sure if it's possible to re-sync RAID1/10 with a simple balance [possibly even without remounting and doing manual device delete/add?] or the filesystem has to be recreated from scratch [like RAID5].) I think this hotplug problem is an entirely different issue from the RAID56-scrub race-conditions (which are now considered fixed in linux 4.12) and nobody is currently working on this (if it's RAID56-only then I don't expect it anytime soon [think years]). -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
