On Fri, Jul 14 2017, Veljko wrote: > 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. You were right to check. md2 is 5761631232 kilobytes, not sectors. so 5626593 (binary) megabytes (exactly) So command should be >> dd if=/dev/md2 of=SOMEWHERE/SAFE bs=1M skip=5626590 and expect it to create a 3M file. Use this 'skip' number of the 'seek' number later. NeilBrown > > 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 >>> > > -- > 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
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