zpool CKSUM 0 --> 1 while resilvering

[Janos Dohanics]

Hello,

I had to replace a hard drive which has failed a smart test. As the
replacement hard drive was being resilvered, I have peridically checked
the progress.

Initially, everything looked fine:

# zpool status
  pool: zroot
 state: ONLINE
status: One or more devices is currently being resilvered.  The pool will
	continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
  scan: resilver in progress since Sun Feb 14 20:44:20 2021
	1.77T scanned at 291M/s, 179G issued at 28.7M/s, 1.97T total
	179G resilvered, 8.88% done, 0 days 18:12:23 to go
config:

	NAME             STATE     READ WRITE CKSUM
	zroot            ONLINE       0     0     0
	  mirror-0       ONLINE       0     0     0
	    ada0p3       ONLINE       0     0     0
	    replacing-1  ONLINE       0     0     0
	      ada1p3     ONLINE       0     0     0
	      ada3p3     ONLINE       0     0     0
	    ada2p3       ONLINE       0     0     0

errors: No known data errors

But a little later CKSUM changed from 0 to 1:

# zpool status
  pool: zroot
 state: ONLINE
status: One or more devices is currently being resilvered.  The pool will
	continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
  scan: resilver in progress since Sun Feb 14 20:44:20 2021
	1.84T scanned at 249M/s, 275G issued at 36.5M/s, 1.97T total
	275G resilvered, 13.65% done, 0 days 13:35:00 to go
config:

	NAME             STATE     READ WRITE CKSUM
	zroot            ONLINE       0     0     0
	  mirror-0       ONLINE       0     0     0
	    ada0p3       ONLINE       0     0     0
	    replacing-1  ONLINE       0     0     0
	      ada1p3     ONLINE       0     0     0
	      ada3p3     ONLINE       0     0     1
	    ada2p3       ONLINE       0     0     0

errors: No known data errors

After resilvering has finished:

# zpool status
  pool: zroot
 state: ONLINE
status: One or more devices has experienced an unrecoverable error.  An
	attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
	using 'zpool clear' or replace the device with 'zpool replace'.
   see: http://illumos.org/msg/ZFS-8000-9P
  scan: resilvered 1.97T in 0 days 08:25:27 with 0 errors on Mon Feb 15 05:09:47 2021
config:

	NAME        STATE     READ WRITE CKSUM
	zroot       ONLINE       0     0     0
	  mirror-0  ONLINE       0     0     0
	    ada0p3  ONLINE       0     0     0
	    ada3p3  ONLINE       0     0     1
	    ada2p3  ONLINE       0     0     0

errors: No known data errors

No errors reported by smartctl(8) for /dev/ada3.

Can I consider this a harmless error and should I just run "zpool clear
ada3p3'?

Please advise.

-- 
Janos Dohanics