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diff --git a/debian/README.recipes b/debian/README.recipes new file mode 100644 index 0000000..3906629 --- /dev/null +++ b/debian/README.recipes @@ -0,0 +1,168 @@ +mdadm recipes +============= + +The following examples/recipes may help you with your mdadm experience. I'll +leave it as an exercise to use the correct device names and parameters in each +case. You can find pointers to additional documentation in the README.Debian +file. + +Enjoy. Submissions welcome. + +The latest version of this document is available here: + http://git.debian.org/?p=pkg-mdadm/mdadm.git;a=blob;f=debian/README.recipes;hb=HEAD + +The short options used here are: + + -l Set RAID level. + -n Number of active devices in the array. + -x Specify the number of spare (eXtra) devices in the initial array. + +0. create a new array +~~~~~~~~~~~~~~~~~~~~~ + mdadm --create -l1 -n2 -x1 /dev/md0 /dev/sd[abc]1 # RAID 1, 1 spare + mdadm --create -l5 -n3 -x1 /dev/md0 /dev/sd[abcd]1 # RAID 5, 1 spare + mdadm --create -l6 -n4 -x1 /dev/md0 /dev/sd[abcde]1 # RAID 6, 1 spare + +1. create a degraded array +~~~~~~~~~~~~~~~~~~~~~~~~~~ + mdadm --create -l5 -n3 /dev/md0 /dev/sda1 missing /dev/sdb1 + mdadm --create -l6 -n4 /dev/md0 /dev/sda1 missing /dev/sdb1 missing + +2. assemble an existing array +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + mdadm --assemble --auto=yes /dev/md0 /dev/sd[abc]1 + + # if the array is degraded, it won't be started. use --run: + mdadm --assemble --auto=yes --run /dev/md0 /dev/sd[ab]1 + + # or start it by hand: + mdadm --run /dev/md0 + +3. assemble all arrays in /etc/mdadm/mdadm.conf +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + mdadm --assemble --auto=yes --scan + +4. assemble a dirty degraded array +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + mdadm --assemble --auto=yes --force /dev/md0 /dev/sd[ab]1 + mdadm --run /dev/md0 + +4b. assemble a dirty degraded array at boot-time +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + If the array is started at boot time by the kernel (partition type 0xfd), + you can force-assemble it by passing the kernel boot parameter + + md-mod.start_dirty_degraded=1 + +5. stop arrays +~~~~~~~~~~~~~~ + mdadm --stop /dev/md0 + + # to stop all arrays in /etc/mdadm/mdadm.conf + mdadm --stop --scan + +6. hot-add components +~~~~~~~~~~~~~~~~~~~~~ + # on the running array: + mdadm --add /dev/md0 /dev/sdc1 + + # if you add more components than the array was setup with, additional + # components will be spares + +7. hot-remove components +~~~~~~~~~~~~~~~~~~~~~~~~ + # on the running array: + mdadm --fail /dev/md0 /dev/sdb1 + + # if you have configured spares, watch /proc/mdstat how it fills in + mdadm --remove /dev/md0 /dev/sdb1 + +8. hot-grow a RAID1 by adding new components +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + # on the running array, in either order: + mdadm --grow -n3 /dev/md0 + mdadm --add /dev/md0 /dev/sdc1 + + # note: without growing first, additional devices become spares and are + # *not* synchronised after the add. + +9. hot-shrink a RAID1 by removing components +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + mdadm --fail /dev/md0 /dev/sdc1 + mdadm --remove /dev/md0 /dev/sdc1 + mdadm --grow -n2 /dev/md0 + +10. convert existing filesystem to RAID 1 +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + # The idea is to create a degraded RAID 1 on the second partition, move + # data, then hot add the first. This seems safer to me than simply to + # force-add a superblock to the existing filesystem. + # + # Assume /dev/sda1 holds the data (and let's assume it's mounted on + # /home) and /dev/sdb1 is empty and of the same size... + # + mdadm --create /dev/md0 -l1 -n2 /dev/sdb1 missing + + mkfs -t <type> /dev/md0 + mount /dev/md0 /mnt + + tar -cf- -C /home . | tar -xf- -C /mnt -p + + # consider verifying the data + umount /home + umount /mnt + mount /dev/md0 /home # also change /etc/fstab + + mdadm --add /dev/md0 /dev/sda1 + + Warren Togami has a document explaining how to convert a filesystem on + a remote system via SSH: http://togami.com/~warren/guides/remoteraidcrazies/ + +10b. convert existing filesystem to RAID 1 in-place +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + In-place conversion of /dev/sda1 to /dev/md0 is effectively + + mdadm --create /dev/md0 -l1 -n2 /dev/sda1 missing + + however, do NOT do this, as you risk filesystem corruption. + + If you need to do this, first unmount and shrink the filesystem by + a megabyte (if supported). Then run the above command, then (optionally) + again grow the filesystem as much as possible. + + Do make sure you have backups. If you do not yet, consider method (10) + instead (and make backups anyway!). + +11. convert existing filesystem to RAID 5/6 +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + # See (10) for the basics. + mdadm --create /dev/md0 -l5 -n3 /dev/sdb1 /dev/sdc1 missing + + #mdadm --create /dev/md0 -l6 -n4 /dev/sdb1 /dev/sdc1 /dev/sdd1 missing + mkfs -t <type> /dev/md0 + mount /dev/md0 /mnt + + tar -cf- -C /home . | tar -xf- -C /mnt -p + + # consider verifying the data + umount /home + umount /mnt + mount /dev/md0 /home # also change /etc/fstab + + mdadm --add /dev/md0 /dev/sda1 + +12. change the preferred minor of an MD array (RAID) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + # you need to manually assemble the array to change the preferred minor + # if you manually assemble, the superblock will be updated to reflect + # the preferred minor as you indicate with the assembly. + # for example, to set the preferred minor to 4: + mdadm --assemble /dev/md4 /dev/sd[abc]1 + + # this only works on 2.6 kernels, and only for RAID levels of 1 and above. + # for other MD arrays, you need to specify --update explicitly: + mdadm --assemble --update=super-minor /dev/md4 /dev/sd[abc]1 + + # see also item 12 in the FAQ contained with the Debian package. + + -- martin f. krafft <madduck@debian.org> Fri, 06 Oct 2006 15:39:58 +0200 |