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Issue adding drive 4 to ReadyNAS nv+ v2
All I recently setup my ReadyNAS NV+ v2 from scratch with 3 3 TB Hitachi DK7SAD300 drives. The steps I followed and an issue I encountered are described in Best way to swap drives ReadyNAS nv+ ...
Good news, I've just completed the factory reset.
What was awkward was that the setup from RAIDar took quite some time; at some point it had to perform a repair synchronising volume c across to disk 4. But after it completed 14 hrs later, I now see a net capacity of 8.1 TB.
Very pleased to see this, I immediately installed the ssh add-on to confirm the RAID volumes are all in good shape. And they are!
No idea why this was so difficult, but very pleased that it's now all working!
root@vanrun:~# mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Fri Feb 27 21:38:08 2026
Raid Level : raid1
Array Size : 4193268 (4.00 GiB 4.29 GB)
Used Dev Size : 4193268 (4.00 GiB 4.29 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sat Feb 28 15:07:38 2026
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Name : 2CB05DBE90E2:0
UUID : 62d0bf22:792a8fc7:22dd1b9f:70d34a1d
Events : 18701
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
2 8 33 2 active sync /dev/sdc1
3 8 49 3 active sync /dev/sdd1
root@vanrun:~# mdadm --detail /dev/md1
/dev/md1:
Version : 1.2
Creation Time : Fri Feb 27 21:38:09 2026
Raid Level : raid6
Array Size : 1048448 (1024.05 MiB 1073.61 MB)
Used Dev Size : 524224 (512.02 MiB 536.81 MB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sat Feb 28 15:03:34 2026
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Name : 2CB05DBE90E2:1
UUID : 843210da:82866fb2:20fe9997:a60abdf5
Events : 111
Number Major Minor RaidDevice State
0 8 2 0 active sync /dev/sda2
1 8 18 1 active sync /dev/sdb2
2 8 34 2 active sync /dev/sdc2
3 8 50 3 active sync /dev/sdd2
root@vanrun:~# mdadm --detail /dev/md2
/dev/md2:
Version : 1.2
Creation Time : Fri Feb 27 21:38:09 2026
Raid Level : raid5
Array Size : 8776634112 (8370.05 GiB 8987.27 GB)
Used Dev Size : 2925544704 (2790.02 GiB 2995.76 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sat Feb 28 15:07:59 2026
State : active
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Name : 2CB05DBE90E2:2
UUID : 2eb52944:e890074d:fc59156f:99b14a04
Events : 905
Number Major Minor RaidDevice State
0 8 3 0 active sync /dev/sda3
1 8 19 1 active sync /dev/sdb3
2 8 35 2 active sync /dev/sdc3
3 8 51 3 active sync /dev/sdd3
Thanks StephenB obviously I am trying to avoid having to do a factory default with all 4 disks in place (as it would require another copy of the approximately 2.6 TB of data to be taken). And yes, I referred to that as (c) / destructive install of the OS.
So I think I understand the behavior now, any hot adding of a disk is destructive (disk will be formatted and new partitions created - followed by a sync). A cold add would be different, i.e. if you power down your NAS remove a disk to (say) add a partition and insert it again before powering it on it would not trigger a format operation and creation of fresh partitions.
I was considering (a) while from the NAS itself, i.e. without adding/removing any of the disks. Based on what we're seeing though, it indeed appears that the NAS somehow does not create the third partition for a reason. Could this be because we would otherwise exceed the size of the md2 volume?
Thinking about the fresh install I performed, I recall it created the volume md2 and next performed a sync. Maybe it created the volume with two drives, adding the third drive through the sync shortly afterwards? That would imply that the capacity of the md2 volume started at the size of a single disk (2.7 TB). I recall as per
Maximum disk size for ReadyNAS NV+ V2 | NETGEAR Communities
that volumes cannot increase by more than 8 TB from their size at creation, nor can they increase beyond 16 TB regardless. Could it be that disk 4 takes us from a raw volume capacity of 2.7 TB to 10.8 TB (i.e. in excess of the max 8 TB increase)?
I always thought this all applied to net capacity of a volume; in that case we would only be hitting the limit if our starting volume size would have been 2.7 TB. I recall having three out of four drives installed in the NAS when I installed it from scratch using the RAIDar software. But not sure now, I think the original logs in /var/log might already have gone?
I believe it would be helpful if we could see whether we are hitting a maximum or not somehow from a log. I.e. an explanation for why the third partition of a hotly added disk never gets created.
A cold add would be different, i.e. if you power down your NAS remove a disk to (say) add a partition and insert it again before powering it on it would not trigger a format operation and creation of fresh partitions.
Not necessarily different. If the NAS detects the disk as new (unformatted or not already in the volume), it goes through the same process. And it normally will do that with cold add.
If you want to try to create the partition manually, it'd be best to do with with the NAS running, and then manually enter the commands to expand the RAID group and then the file system.
Maximum disk size for ReadyNAS NV+ V2 | NETGEAR Communities
that volumes cannot increase by more than 8 TB from their size at creation, nor can they increase beyond 16 TB regardless. Could it be that disk 4 takes us from a raw volume capacity of 2.7 TB to 10.8 TB (i.e. in excess of the max 8 TB increase)?Your logs show three disks on 31 January, I have no way to see anything before that.
But even if you started with 1 disk installed, the total gain in volume size would be 6 TB (5.45 TiB). The limits are not computed from raw disk sizes. A single 3 TB drive would give you a 2.7 TiB volume size, and a 4x3TB RAID-5 setup gives you an 8.18 TiB volume size.
So you are not hitting any of the expansion limits.
obviously I am trying to avoid having to do a factory default with all 4 disks in place (as it would require another copy of the approximately 2.6 TB of data to be taken).
I get that, but I still think that is the right next step.
31 Jan is when I installed the NAS from scratch using RAIDar. And looking through /var/log/frontview/md_expand.log, it appears that the NAS also keeps track of serial numbers of the drives.
Good to know that I am not hitting the expansion limits.
And starting from scratch with option (c) indeed seems to be the right choice unfortunately!
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