On 07/14/2017 03:57 AM, NeilBrown wrote:
Presumably you also have an md3 raid10 which you want to attach to the end of md2?
Yes, I just created it. It's resyncing.
md2 is 5761631232 sectors. 2880815616 kilobytes 2813296.5 (binary)megabytes. When you include that into a "linear" you will lose a few K from the end. It might be sensible to cause the "linear" to use whole stripes from the raid10, where a stripe is 1M (2 512K chunks). If you did that, you would lose a little over 1M. So backup the last 3.5 M of the raid10. This is much more than you need. ie. dd if=/dev/md2 of=SOMEWHERE/SAFE bs=1M skip=2813293
I'm little confused. What I'm backuping is last 3.5M of used space, right? How is that only ~2.7T? df shows 4.8T of used space.
Rest of the instructions are clear and I'll try it as soon as md3 is synced.
Thanks Neil!
(dd treats 'M' as 1024*1024, MB is 1000*1000) If the file this creates is not 3.5M, then something went wrong. Stop here. Just to be safe you might want to backup the first few megabytes. You won't need this unless something goes wrong dd if=/dev/md2 of=SOMEWHERE/ELSE bs=1M count=10 Now create the linear from /dev/md2 and /dev/md3(?). Be sure to use "-e 1.0 --data-offset=0". This creates /dev/md4 Now restore the first backup dd if=SOMEWHERE/SAFE of=/dev/md4 bs=1M seek=2813293 Be sure to use the same bs= and seek= as you did the first time. Be sure it is copying from the back and to the new linear raid. You should now be done. Check your xfs filesystem, and maybe even mount it and use it. NeilBrown# mdadm --detail /dev/md2 /dev/md2: Version : 1.2 Creation Time : Fri Sep 14 12:40:13 2012 Raid Level : raid10 Array Size : 5761631232 (5494.72 GiB 5899.91 GB) Used Dev Size : 2880815616 (2747.36 GiB 2949.96 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Mon Jul 10 12:32:51 2017 State : clean Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Layout : near=2 Chunk Size : 512K
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