Thank you both for your input. see below.
> > You sda and sdb are at gen 60233 while sdd and sde are at gen 60234. > > It's possible to allow kernel to manually assemble its device list using > > "device=" mount option. > > Since you're using RAID6, it's possible to recover using 2 devices only, > > but in that case you need "degraded" mount option. > > He has btrfs raid0 profile on top of hardware RAID6 devices. Correct, my FS is a "raid0" across four hardware-raid based raid6 devices. The underlying devices of the raid controller are fine, same as the volumes themselves. Only corruption seems to be on the btrfs side. Does your tip regarding mounting by explicitly specifying the devices still make sense? Will this figure out automatically which generation to use? I am at the moment in the process of using "btrfs restore" to pull more data from the filesystem without making any further changes. After that I am happy to continue testing, and will happily test your mentioned "skip_bg" patch - but if you think that there is some other way to mount (just for recovery purpose - read only is fine!) while having different gens on the devices, I highly appreciate it. Thanks Qu and Andrei!
