Tried with the /dev/mapper/sdx devices. root@superior:/mnt/backup# mdadm --create /dev/md0 --level=raid6 -n 6 /dev/mapper/sdb /dev/mapper/sdc /dev/mapper/sdd /dev/mapper/sde /dev/mapper/sdf /dev/mapper/sdg mdadm: partition table exists on /dev/mapper/sdb mdadm: partition table exists on /dev/mapper/sdc mdadm: partition table exists on /dev/mapper/sdc but will be lost or meaningless after creating array mdadm: partition table exists on /dev/mapper/sdd mdadm: partition table exists on /dev/mapper/sdd but will be lost or meaningless after creating array mdadm: partition table exists on /dev/mapper/sde mdadm: partition table exists on /dev/mapper/sde but will be lost or meaningless after creating array mdadm: partition table exists on /dev/mapper/sdf mdadm: partition table exists on /dev/mapper/sdf but will be lost or meaningless after creating array mdadm: partition table exists on /dev/mapper/sdg mdadm: partition table exists on /dev/mapper/sdg but will be lost or meaningless after creating array Continue creating array? n mdadm: create aborted. root@superior:/mnt/backup# Chickened out and aborted the create. Are those expected messages for the mess I am in? And the victory conditions would be a mountable file system that passes a fsck? On Mon, Aug 29, 2022 at 7:53 PM Peter Sanders <plsander@xxxxxxxxx> wrote: > > Couple more questions. > > Mdadm -create ... Do I use the /dev/sdx or /dev/mapper/sdx name for > the overlayed device? > > And reset the mapping between each create attempt by doing: > remove the loop-device/overlay association > dmsetup remove on all devices > remove the overlay files > rm > remove the loop back devices > losetup -d ... > rebuild the loop back devices > mknod -m 660 ... > build the overlay files > truncate -s 300G overlay-... > reassociate the loop-devices and the overlays > losetup... dmsetup.. > > and try again. > > (Yeah, I recognize that there is code to do this (I think) in the > article, but my script-fu is not up to fully understanding those > examples.) > > On Mon, Aug 29, 2022 at 6:58 PM Eyal Lebedinsky <fedora@xxxxxxxxxxxxxx> wrote: > > > > > > On 30/08/2022 07.45, John Stoffel wrote: > > >>>>>> "Peter" == Peter Sanders <plsander@xxxxxxxxx> writes: > > > > > > Peter> Phil, > > > Peter> fstab from the working config - > > > > > > Peter> # <file system> <mount point> <type> <options> <dump> <pass> > > > Peter> # / was on /dev/sda1 during installation > > > Peter> UUID=50976432-b750-4809-80ac-3bbdd2773163 / ext4 > > > Peter> errors=remount-ro 0 1 > > > Peter> # /home was on /dev/sda6 during installation > > > Peter> UUID=eb93a2c4-0190-41fa-a41d-7a5966c6bc47 /home ext4 > > > Peter> defaults 0 2 > > > Peter> # /var was on /dev/sda5 during installation > > > Peter> UUID=d1aa6d1f-3ee9-48a8-9350-b15149f738c4 /var ext4 > > > Peter> defaults 0 2 > > > Peter> /dev/sr0 /media/cdrom0 udf,iso9660 user,noauto 0 0 > > > Peter> /dev/sr1 /media/cdrom1 udf,iso9660 user,noauto 0 0 > > > Peter> # raid array > > > Peter> /dev/md0 /mnt/raid6 ext4 defaults 0 2 > > > > > > Peter> No LVM, one large EXT4 partition > > > > > > Peter> I have several large files ( NEF and various mpg files) I can identify > > > Peter> and have backup copies available. > > > > > > Peter> I have the overlays created. 300G for each of the six drives. > > > > > > So that's good. Now you have to try and figure out which order they > > > were created in. As the docs show, you setup the overlayfs on top of > > > each of the six drives. > > > > > > Keep track by noting the drive serial numbers, since Linux can move > > > them around and change drive letters on reboots. > > > > > > > > > Then using the overlays, do an: > > > > > > mdadm --create /dev/md0 --level=raid6 -n 6 /dev/sd[bcdefg] > > > fsck -n /dev/md0 > > > > > > and see what you get. If it doesn't look like a real filesystem, then > > > you can break it down, and then modify the order you give the drive > > > letters, like: > > > > > > /dev/sd[cdefge] > > > > > > and rinse and repeat as it goes. Not fun... but should hopefully fix > > > things for you. > > > > > > John > > > > An aside, I would think the way to specify a list in a nominated order is something like > > > > $ echo /dev/sd{c,d,a,b} > > /dev/sdc /dev/sdd /dev/sda /dev/sdb > > > > rather than > > > > $ echo /dev/sd[cdab] > > /dev/sda /dev/sdb /dev/sdc /dev/sdd > > > > which will be in sorting order, regardless of the order of the letter. > > > > -- > > Eyal Lebedinsky (fedora@xxxxxxxxxxxxxx)