On Tuesday August 10, philip@xxxxxxxxxxxxxx wrote: > Neil Brown wrote: > > > On Tuesday August 10, philip@xxxxxxxxxxxxxx wrote: > > > >>Linux RAID *has* to have sort of way to force a parity resync. If it > >>doesn't have one, it needs one. That's a glaring omission to make. > > > > Well, you get what you pay for..... > > Tell me where to send the checks. Seriously. I know you guys work hard > on this stuff and I will gladly donate to the fund to have important (to > me) features implemented. Hmmm. Awkward. I'm not averse to doing a bit of contracting at times (taking un-paid leave or similar from my day job), but having a fund that people can donate to might be a bit more awkward... > > > The easiest way to force a resync would be to re-create the array. > > > > - Note the exact order of the drives in the array, and the chunk size. > > - Stop the array. > > - Create the array with mdadm using --force. That bit is important. > > Do I need to note the parity algorithm, too? Yes, though I strongly suspect the array was created with the default parity algorithm, so it shouldn't make any difference. > > > mdadm --create /dev/mdX --level=5 --force --disks=whatever \ > > --chunksize=64k /dev/sda1 /dev/sdb1 ..... > > > > Remember the --force. If you don't have it, you will get a recovery > > cycle that rebuilds one drive against the others rather than a resync > > that checks and corrects parity. > > > > This will recreate the array (almost) exactly as it currently is, but > > it will not be marked 'clean', so a parity check-and-correct will > > happen. > > Does this destroy the data on the array? I seem to remember getting > this advice a while back when encountering a similar problem and seeing > my data go up in smoke. I could easily have done something wrong, though. No, it doesn't destroy the data - provided you have the configuration exactly the same as before. It will only update the superblocks and correct all parity blocks. Data blocks won't be changed. However I have just release mdadm 1.7.0 which supports --assemble --update=resync which will cause an array to resync immediately after being assembling. This don't help you for an array with a root filesystem on it, but should do want you want for any other array. NeilBrown - 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
