Hi Neil, Nice work on the Bus1 article! On Sat, Aug 20, 2016 at 07:26:27AM +1000, NeilBrown wrote: > On Fri, Aug 19 2016, Chris Dunlop wrote: >> In my case, I want it to write everything. >> >> If I do my 'dd' to write everything as previously described, with the window >> of opportunity for stale data to end up on the written disk, one option >> would to run a scrub / repair to check the data is the same - but if I'm >> unlucky with my dd and the data isn't the same for some sector[s], I want to >> ensure the correct data is copied over the stale data and not the other way >> around, e.g. to specify "in the event of a mismatch, use the data from sda >> and overwrite the data on sdb". >> >> Unfortunately I don't know how that can be done. >> >> Does anyone know? > > If it is the second device in the array (as listed by mdadm --detail) > then you can stop the array and re-assemble with --update=resync. That's nearly there - except in this specific case it's my root filesystem so I can't stop the array without booting into a recovery disk etc. Of course I could do that, but the point of the exercise is to see if it can be done live, safely. > If it is the first device I can only suggest that you > fail the device and add it again: > > mdadm /dev/mdXX --fail /dev/sdYY > mdadm /dev/mdXX --remove /dev/sdYY > mdadm /dev/mdYY --add /dev/sdYY > > If the "good" drive fails during the rewrite it might be a little bit > fiddley getting the array working again, but all the data will certainly > be there on the device you are re-writing, so you won't lose anything. OK, that sounds good. What would the process be if the good drive fails, either completely, or a few specific sectors? Thanks, Chris -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
