ZFS resilver from disk with bad sectors constantly restarts

[Steven Hartland]

Ignore my last post just noticed you 9.1 at the end, which is very old, 
so it could well be this is already fixed; only way to confirm is 
upgrade an check ;-)

     Regards
     Steve

On 30/10/2015 10:36, Dmitry Marakasov wrote:
> Hi!
>
> I've just got a case where resilvering a new replacement disk in raidz2
> never finished.
>
> The problem: one disk in raidz is failing by having a large number of
> unreadable sectors. It's replaced with a spare. Resilver though is
> constantly restarted with log full of read error from bad disk.
>
> It looks like this:
>
> ---
>    pool: spool
>   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 Wed Oct 28 05:26:28 2015
>          369G scanned out of 9,87T at 123M/s, 22h29m to go
>          41,4G resilvered, 3,65% done
> config:
>
> 	NAME                  STATE     READ WRITE CKSUM
> 	spool                 ONLINE       0     0     0
> 	  raidz1-0            ONLINE       0     0     0
> 	    ada0              ONLINE       0     0     0
> 	    ada1              ONLINE       0     0     0
> 	    spare-2           ONLINE       0     0   733
> 	      ada11           ONLINE       0     0     0
> 	      ada2            ONLINE       0     0     0  (resilvering)
> 	  raidz1-1            ONLINE       0     0     0
> 	    ada3              ONLINE       0     0     0
> 	    ada4              ONLINE       0     0     0
> 	    ada5              ONLINE       0     0     0
> 	  raidz1-2            ONLINE       0     0     0
> 	    ada6              ONLINE       0     0     0
> 	    ada7              ONLINE       0     0     0
> 	    ada10             ONLINE       0     0     0
> 	spares
> 	  588540573008830286  INUSE     was /dev/ada2
>
> errors: No known data errors
> ---
>
> `resilver in progress since' date is constantly reset, so resilved
> progress cannot pass beyond 5% or so. My guess is that it happens on
> read errors on ada11. I think I've seen (resilvering) on ada11 line
> couple of times.
>
> In the end I've had to offline ada11 and after that resilver completed
> in under 16 hours. However the situation doesn't seem normal, as I'd
> prefer to not lose redundancy with offlining dying disk and still be
> able to use it for resilvering (imagine there were bad sectors on ada0/1
> as well, but not intersecting with bad sectors on ada11), or at least
> some more verbose indication of why the resilver is constantly restarted.
>
> I should also note that's outdated FreeBSD 9.1, so maybe that problem
> was fixed already.
>