On Wed, Jun 24, 2009 at 06:20, NeilBrown<neilb@xxxxxxx> wrote: > On Wed, June 24, 2009 8:27 pm, Michael Ole Olsen wrote: >> Is it possible to reshape my /dev/md0 raid5 into raid6? > > If you are are using Linux 2.6.30, then you can > > echo raid6 > /sys/block/md0/md/level > > and it will instantly be sort-of-raid6. > It is exactly like raid6 except that the Q blocks are all one > the one drive, and drive that previously didn't exist. > If you have a spare, it will start building the Q blocks > on that drive and when it finishes you will have true raid6 > redundancy, though possibly a little less than raid6 performance, > as a real raid6 has the Q block distributed. > > When mdadm-3.1 is released, you will be able to tell the raid6 > to re-stripe with a more traditional layout. This will take quite > a while, but you can continue to use the array (though a bit more > slowly) will it progresses. > Of course you don't need to do that step if you don't want to. I have a raid5 array on 2.6.18 that I'd like to grow like this. I might wait until mdadm-3.1 so I can stripe Q from the git-go. I'd like to --stop the array on the 2.6.18 machine, and export the individual disks over iscsi to a 2.6.30 machine, and use the newer mdadm there to grow the array from raid5 to raid6. Then --stop it on the 2.6.30 machine, unexport the disks, and --start the array again on the 2.6.18 machine. Disclaimers aside, should that work? My main concern is 2.6.18's ability to work with this 'creative' raid6 implementation that currently results from the grow from raid5 to raid6. I've also got a few disks to add, so maybe the better solution would be to add one and get the unstriped Q, then add another and let Q stripe with everything else during the reshape. That is, if it will stripe Q during the reshape. -- 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
