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Help! Volume crashed.


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So, I was forced to do a reboot during expansion. My drives are 2/2/2/3/3/4/4. Rebooted in the middle of expanding the last 4 TB drive.


More detailed information can be found here: http://forum.synology.com/enu/viewtopic ... 9&t=109329


Essentially, what I should have is:


md2 in raid5 with 7x2TB partitions

md3 in raid5 with 4x1TB partitions

md4 in raid1 with 2x1TB partitions


The system was rebooted during reshape of md2. Upon power up, I find that md4 was created and md2 automatically assembled and finished reshape and resync.


md3 failed to assemble.


Recreating the situation in VirtualBox, I was able to recover by recreating md3.


1. I got the order of the drives via the mdadm -A --scan --verbose command. It reports which partitions were in which slot of md3.

2. I got the size by doing mdadm --examine /dev/sdb6, where sdb6 is a partition that was in the array. I then took that number and divided by 2 to convert from 512b blocks to 1024b blocks.

3. I recreated the array via: mdadm --create --assume-clean --level=5 --raid-devices=3 /dev/md3 /dev/sd[abc]6, where I passed the 3 members in the same order as the first three members of the array (slots 0-2).

4. vgchange -a y

5. mount /dev/vg1000/lv /mnt


It also appeared to work if I specified the drives in any order.

AND, it also appeared to work if I recreated the array with all 4 drives (with --raid-review=4)


I am too afraid to run this on th actual NAS. Looking for some confirmation to say that this is the correct way for me to recover the data.


Note, I did try to force assembly, but got an error about being in a critical section and needing a backup file, which I do t hav.


I've posted on Synology forums, Linux-raid mailing list, but have not gotten any responses.


Please help! Thank you in advance


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