Hi, >> I have a a few two-disk RAID1 partitions that I'd like to convert to >> three-disk RAID5 partitions using fedora15 with ext4. I've read a few >> docs online, but none that are authoritative or current. Some even say >> to zero the superblock first, which doesn't sound safe at all. ... >> Is the general process to first convert the RAID1 to a two-disk RAID5, >> then --add the third disk? > > I strongly suggest that you create a couple of loop-back devices and > experiment. > ie. > > for i in 0 1 2 > do > dd if=/dev/zero of=/tmp/file$i bs=1M count=100 > losetup /dev/loop$i /tmp/file$i > done > > mdadm -C /dev/md0 -l1 -n2 -e 1.0 /dev/loop0 /dev/loop1 > mkfs /dev/md0 > mount /dev/md0 /mnt > cp -r /lib /mnt > > then try some things. e.g. > > mdadm /dev/md0 --add /dev/loop2 > mdadm --grow /dev/md0 --level=5 --raid-devices=3 > > Try failing a device during the reshape. Check if the data is still OK. > Try it as two separate steps and see if it makes a difference. > > Experimenting will give you a lot more confidence than any mount of > authoritative statements about what it should do. Yes, definitely. I have an understanding now of what needs to be done, and am comfortable with mdadm, just not this procedure. I've followed your steps and they worked successfully. I just wasn't sure from my reading whether this was a supported procedure, or whether there were still experimental steps required. > There was once a tool called raidreconf which would reshape an array while it > is offline. That isn't supported anymore. Yes, I came across that as well, but sounds like it's just not necessary any longer because it's so well supported in mdadm itself, correct? Thanks, Alex -- 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
