On Sep 10, 2014, at 7:27 PM, NeilBrown wrote: > On Wed, 10 Sep 2014 11:15:24 -0500 Michael Muratet <muratetm@xxxxxxxxx> wrote: > >> I have a two-disk RAID0 system that is working splendidly, thanks to the list for the help. >> >> I managed to get my hands on more identical disks and since I have the disks and because I'm adding precious data, I'd like to add two more disks and grow to RAID5. >> >> I have partitioned the two new drives to type 'fd', /dev/sde and /dev/sdf >> >> I believe the command to accomplish the change is this: >> >> mdadm /dev/md0 --grow --level=5 --add /dev/sde /dev/sdf >> >> Following the old adage "measure twice, cut once", is this syntax correct? Is there any danger of data loss in such a conversion? > > I recommend creating a few loop-back devices and experimenting. > i.e.: > create some 100M files. > use "losetup" to turn them into block devices. > create an 2-device raid0 > try converting it as you suggest. > > You find it doesn't do quite what you expected, but should be easy to fix. In case anyone wants to do a similar thing... As predicted, it did not do as I expected. I have another identical server and disks and so I did the experiment there. 980 sudo fdisk /dev/sdc 981 sudo fdisk /dev/sdd 982 sudo fdisk /dev/sde 983 sudo fdisk /dev/sdf 988 sudo partprobe /dev/sdc 989 sudo partprobe /dev/sdd 990 sudo partprobe /dev/sde 991 sudo partprobe /dev/sdf 995 sudo mdadm --create /dev/md0 --level=0 --raid-disk=2 /dev/sdc1 /dev/sdd1 996 sudo mkfs -t ext3 /dev/md0 997 sudo mount -t ext3 /dev/md0 /db Same RAID0 system I created before. Now to grow 1004 sudo mdadm /dev/md0 --grow --level=5 --add /dev/sde1 /dev/sdf1 Makes a RAID5 system, but sde1 was added as a spare 1022 sudo mdadm --grow /dev/md0 --raid-devices=4 It's now a four disk RAID, but smaller than expected. It spread the original space over four drives, which I think is the documented behavior. 1040 sudo umount /dev/md0 1045 sudo e2fsck -f /dev/md0 1046 sudo resize2fs -p /dev/md0 1048 sudo mount -t ext3 /dev/md0 /db 1049 df -h /dev/md0 2.7T 202M 2.6T 1% /db which is what I wanted. I can't take my original system offline now, but when I can I will apply the same steps. Thanks for the help Cheers Mike > > Providing your new devices are reliable (as least read/write the entire drive > once if you feel at all cautious) there is no particular danger of data loss. > > NeilBrown > > >> >> Thanks >> >> Mike-- >> 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 > -- 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
