Duncan posted on Tue, 23 Feb 2016 23:17:06 +0000 as excerpted:

Marc MERLIN posted on Tue, 23 Feb 2016 13:59:11 -0800 as excerpted:

quoted

I have a freshly created md5 array, with drives that I specifically
scanned one by one block by block, and for good measure, I also scanned
the entire software raid with a check command which took 3 days to run.

Everything passed.

Then, I made a bcache of that device, an ssd that seems to work fine
otherwise (brand new), and dmcrypted the result

md5 - bache - dmcrypt - btrfs ssd /

Now, I'm copying data over with btrfs send, and I'm seeing these slowly
show up and the write counter go up one by one.
BTRFS error (device dm-7): bdev /dev/mapper/oldds1 errs: wr 17, rd 0,
flush 0, corrupt 0, gen 0

Where is the documentation for those counters?
Is the write error fatal, or a recovered error?
Should I consider that my filesystem is corrupted as soon as any of
those counters go up?
(I couldn't find an exact meaning of each of them)

I believe all formal documentation of what the error counters actually
mean is developer-level -- "Trust the Source, Luke."

Forgot to mention, tho you're probably already considering it, if this is 
the same raid5-backed btrfs you were complaining about being slow in the 
other thread, and considering redoing with bcache to an ssd added, as 
seems very likely, if it /is/ actually storage device or bus errors, that 
could be one reason the previous one was getting so slow...  Maybe it 
wasn't btrfs after all.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman