On Sun, 22 Jun 2014, George Duffield wrote:
I've got a RAID5 array comprised of 4 x 3TB drives which is 97% full and would like to grow the array by adding a 5th drive of the same make/ model.
Consider adding two drives and go to RAID6. http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162
Looking at https://raid.wiki.kernel.org/index.php/Growing it seems the approach (after partitioning the drive) is to: 1) add the drive to the pool: # mdadm --add /dev/md127 /dev/sdX1 2) grow the array: # mdadm --grow --raid-devices=5 --backup-file=~/grow_md127.backup /dev/md127
Make sure the backup file is NOT on a filesystem that is on the md being resized. Put it on /root or something instead.
3) edit mdadm.conf to include the 5th drive i.e. num-devices=5 4) determine raid stride size calculated with chunk / block 4) ensure the array is unmounted and resize ext4: # resize2fs -S ascertained_stride_size -p /dev/md127
Yeah, that looks about right. Don't know if you really need step 4, just enmount and resize, I would imagine that if you have a reasonable resent version of the tools it'll figure out the stride size automatically.
You cannot avoid the resync, so stop looking into weird options. The resizing will take days.
-- Mikael Abrahamsson email: swmike@xxxxxxxxx -- 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
