On 2/18/21 3:57 PM, Chris Murphy wrote:

metadata raid6 as well?

Yes.

What replacement command(s) are you using?

For this drive, it was "btrfs replace start -r 3 /dev/sda3 /"

What device is devid 3? 

It would normally be sdc3. I'll address the confusion below.

16315=0x3fbb, 16283=0x3f9b, 16315^16283 = 32 or 0x20
11111110111011
11111110011011
        ^

Do a RAM test for as long as you can tolerate it, or it finds the
defect. Sometimes they show up quickly, other times days.

I didn't think of a flipped bit. Thanks.

quoted

        devid    0 size 457.64GiB used 39.53GiB path /dev/sdc3
        devid    1 size 457.64GiB used 39.56GiB path /dev/sda3
        devid    2 size 457.64GiB used 39.56GiB path /dev/sdb3
        devid    4 size 457.64GiB used 39.53GiB path /dev/sdd3

This is confusing. devid 3 is claimed to be missing, but fi show isn't
showing any missing devices. If none of sd[abcd] are devid 3, then
what dev node is devid 3 and where is it?

It looks to me like btrfs is temporarily assigning devid 0 to the new
device being used as a replacement. That is what I observed before; once
the replace operation was complete, it went back to the normal number.
Since the replacement didn't finish this time, sdc3 is still devid 0.

But yeah you're probably best off not trying to fix this file system
until the memory is sorted out.

Right. I'll get on that soon and see if anything pops up. Thanks for the
help so far.