On Wednesday June 24, billycrook@xxxxxxxxx wrote: > 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. 2.6.18 will not understand the raid6 created by simply echoing 'raid6' in to the 'level' file. It will need to be restriped with the help of mdadm-3.1 first. > > 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. Your best bet would be to wait for mdadm-3.1 and do it all at once, something like: mdadm --grow /dev/md0 --level=raid6 --raid-disks=8 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
