I have a system built on a Linux raid 1 using ext3.
When the system was created there was a large amount of space left available on both of the raid 1 disks for future expansion of a partition as required.
I know expanding the file system using LVM is relatively trivial but this system was not built using LVM.
Is it possible to expand the partitions, expand the RAID 1 to fill the partitions, and then expand the ext3 file system on the RAID1?
It's fairly easy, but tricky the first time you do it. You must have a fairly recent 2.6 kernel and fairly recent raid tools (mdadm, anyway).
I would suggest doing a reboot first, and bring the system back up in single-user mode, BUT this can theoretically be done on a live system. YMMV.
# remove secondary mirror from array mdadm --manage /dev/md0 --fail /dev/hdb1 --remove /dev/hdb1 # resize the partition fdisk /dev/hdb * change hdb1 to be bigger # re-add the partition. MD will automatically use only as much size as /dev/hda1 at this time mdadm --manage /dev/md0 --add /dev/hdb1 * wait for re-sync (watch /proc/mdstat) # remove primary mirror from array mdadm --manage /dev/md0 --fail /dev/hda1 --remove /dev/hda1 # resize the partition fdisk /dev/hda * change hda1 to be bigger # re-add the partition. MD will still only use as much size as the original array mdadm --manage /dev/md0 --add /dev/hda1 * wait for re-sync (watch /proc/mdstat) # NOW we can tell MD to expand the RAID set to fill the underlying block device (hda1/hdb1) mdadm --grow /dev/md0 * wait for re-sync (watch /proc/mdstat) # and now that we have a bigger block device underlying the filesystem, we can resize the filesystem itself resize2fs -p /dev/md0
If you can't do that for whatever reason, see the following complicated set of steps.
Definitely do-able, but scary. Well, sorta. Make sure you have a good backup first. Read the mdadm(8) manpage carefully. Now read it again, you didn't grasp it all the first time - no-one can.
Assuming you're starting out with md0 (root, including boot) as a RAID-1 set across /dev/hda1 and /dev/hdb1:
1. Hot remove hda1 from md0. 2. Delete hda1. 3. Re-create hda1, filling the entire disk. (Make sure it isn't bigger than hdb1 will be in step 11.) 4. Create md1 as RAID-1 across hda1 and a "missing" device. 5. Create new filesystem on md1. 6. Mount md1 to /mnt. 7. Transfer all files: cd / init S dump -0 / | ( cd /mnt ; restore - ) ** or use tar(1), or cpio(1) or whatever works for your filesystem type ** grub-install /dev/md1 ** see my previous post about getting GRUB installed on the non-currently-booted disk (http://www.muug.mb.ca/pipermail/roundtable/2006-April/001086.html) ** umount /dev/md1 8. Reboot (hopefully onto md1 AKA hda1) 9. Stop mdX (whatever hdb1 came up as... likely md0 and md1 got swapped around during the reboot, but check carefully!) 10. Delete hdb1. 11. Re-create hdb1, filling the entire disk. 12. Hot add hdb1 to md0 13. Wait for md-sync to finish (check via /proc/mdstat)
Step 8 is the most problematic - it might be a good idea to have a GRUB boot floppy with a local copy of the grub.conf on the floppy... and a printout of your grub.conf. If you can boot off floppy but not off hda1, you can at least try to correct the problem. If you can't boot at all, well...
Good luck! -Adam
John Lange wrote:
Thanks Adam.
Option 1 looks doable.
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Adam Thompson -
John Lange