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Forum Discussion
X-RAID vertical expansion incomplete
ReadyNAS 314 running OS 6.4.0
Was previously running with 4x1TB drives. As we came close to filling that up, ordered 4x2TB drives for vertical expansion.
Replaced the disk in bay 1, waited for resync to complete, no problems.
Replaced the disk in bay 2, waited for resync to complete, no problems. After that it began a second lengthy operation (I can't remember the exact verbiage used, but I'm fairly confident that this was expanding the capacity to make use of the two newer disks). No problems.
Replaced the disk in bay 3, waited for resync to complete, no problems. Waited for expansion to complete, no problems.
Replaced the disk in bay 4, waited for resync to complete, no problems. I did not immediately notice that the final expansion did not take place.
This unit has SSH enabled, so when I noticed that the capacity wasn't what I expected (it reports 4.45 TB capacity instead of the expected 5.24 TB), I poked around a bit and found this:
root@netgear:~# btrfs filesystem show /data
Label: '5e276904:data' uuid: 7e35ca18-0d2e-45f7-aa31-a82747bea137
Total devices 2 FS bytes used 2.61TiB
devid 1 size 2.71TiB used 2.63TiB path /dev/md127
devid 2 size 1.82TiB used 171.00GiB path /dev/md126
btrfs-progs v4.1.2
root@netgear:~# mdadm --detail /dev/md127
/dev/md127:
Version : 1.2
Creation Time : Tue Jul 9 03:32:40 2002
Raid Level : raid5
Array Size : 2915731968 (2780.66 GiB 2985.71 GB)
Used Dev Size : 971910656 (926.89 GiB 995.24 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Tue Sep 6 17:50:49 2016
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Name : 5e276904:data-0 (local to host 5e276904)
UUID : e33eecc1:f9ec98cf:0bae86e1:28333094
Events : 3594
Number Major Minor RaidDevice State
4 8 3 0 active sync /dev/sda3
5 8 19 1 active sync /dev/sdb3
6 8 35 2 active sync /dev/sdc3
7 8 51 3 active sync /dev/sdd3
root@netgear:~# mdadm --detail /dev/md126
/dev/md126:
Version : 1.2
Creation Time : Tue Aug 9 17:01:44 2016
Raid Level : raid5
Array Size : 1953245824 (1862.76 GiB 2000.12 GB)
Used Dev Size : 976622912 (931.38 GiB 1000.06 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Tue Sep 6 17:50:49 2016
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 64K
Name : 5e276904:data-1 (local to host 5e276904)
UUID : df0953ba:a63f8097:563d7345:af6846f6
Events : 3031
Number Major Minor RaidDevice State
0 8 4 0 active sync /dev/sda4
1 8 20 1 active sync /dev/sdb4
2 8 36 2 active sync /dev/sdc4
3 8 52 - spare /dev/sdd4
root@netgear:~# mdadm --examine /dev/sdd4
/dev/sdd4:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : df0953ba:a63f8097:563d7345:af6846f6
Name : 5e276904:data-1 (local to host 5e276904)
Creation Time : Tue Aug 9 17:01:44 2016
Raid Level : raid5
Raid Devices : 3
Avail Dev Size : 1953245896 (931.38 GiB 1000.06 GB)
Array Size : 1953245824 (1862.76 GiB 2000.12 GB)
Used Dev Size : 1953245824 (931.38 GiB 1000.06 GB)
Data Offset : 262144 sectors
Super Offset : 8 sectors
Unused Space : before=262056 sectors, after=72 sectors
State : clean
Device UUID : 3de39043:50f0af6e:cbcdc324:337612b0
Update Time : Fri Aug 12 01:47:27 2016
Bad Block Log : 512 entries available at offset 72 sectors
Checksum : 1e90ec50 - correct
Events : 3031
Layout : left-symmetric
Chunk Size : 64K
Device Role : spare
Array State : AAA ('A' == active, '.' == missing, 'R' == replacing)It looks like the device kept the original RAID array as-is with the ~3TB storage capactiy in the first 1TB of each drive, built a second RAID 5 array using the next 1TB of each drive, and then used BTRFS features to join them into a single filesystem (which is fine). What I don't understand is why the second RAID array (/dev/md126) is treating the top 1TB of the fourth disk (/dev/sdd4) as a 'spare' rather than an active disk. All four new disks are identical Western Digital Reds.
We have good backups and so in principle I could just wipe the array and start over, however this array is actively used in a business and the associated downtime is not particularly appealing, especially since I'm not often physically on-site with the unit.
Yes, but you do want to check the disks are healthy, partitions are the correct size etc. before doing that.
Doing it yourself is at your own risk.
8 Replies
That's easily fixed.
Btw 6.4.0 is old firmware. Once the problem is fixed you may wish to update the firmware.
- You could try to simply reboot the NAS. Otherwise, I would fail, remove then add sdd4 from/to md126. If you're not comfortable with fixing the RAID yourself, you could try to contact NETGEAR Support.
- Actually, you might just need to grow the number of raid devices of md126 from 3 to 4.
omicron_persei8 wrote:
Actually, you might just need to grow the number of raid devices of md126 from 3 to 4.Assuming everything is fine, yes. Once the RAID is expanded the volume should automatically expand.
mdgm wrote:
omicron_persei8 wrote:
Actually, you might just need to grow the number of raid devices of md126 from 3 to 4.Assuming everything is fine, yes. Once the RAID is expanded the volume should automatically expand.
Am I correct that this would be accomplished simply by running
mdadm --grow /dev/md126 --raid-devices=4
from SSH (assuming the system is in all other ways healthy)? Or are there any special considerations introduced by ReadyNAS or BTRFS?
--- EDIT ---
Nevermind, just saw your PM, mdgm. Thanks for the info, I'll give it a shot after some additional checks.
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