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Forum Discussion
Possible Failed RAID5 to RAID6 Converstion
Hi
I have a RN528X. I moved a 6 drive RAID5 (XRAID2) array from a RN516. This consisted of 4x14TB and 2x10TB. They have been vertically expanded before (6x6TB -> 6x10TB -> replace 4 with 14TB).
I added a 7th disk - 14TB - wanting the redundancy of RAID6.
Looking at this:
root@MediaMaster:~# cat /proc/mdstat
Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md1 : active raid10 sdh2[6] sdf2[5] sde2[4] sdd2[3] sdc2[2] sdb2[1] sda2[0]
1827840 blocks super 1.2 512K chunks 2 near-copies [7/7] [UUUUUUU]
md125 : active raid6 sdh4[10] sda4[9] sdf4[5] sde4[4] sdd4[6] sdc4[7] sdb4[8]
19528915840 blocks super 1.2 level 6, 64k chunk, algorithm 18 [7/6] [UUUUUU_]
[=>...................] reshape = 8.1% (317756860/3905783168) finish=732.7min speed=81611K/sec
md126 : active raid6 sdh3[12] sda3[11] sdf3[7] sde3[6] sdd3[8] sdc3[9] sdb3[10]
29278364160 blocks super 1.2 level 6, 64k chunk, algorithm 2 [7/7] [UUUUUUU]
md127 : active raid5 sdh5[4] sdc5[0] sda5[3] sdb5[2] sdd5[1]
15623254016 blocks super 1.2 level 5, 64k chunk, algorithm 2 [5/5] [UUUUU]
md0 : active raid1 sdh1[12] sda1[11] sdf1[7] sde1[6] sdd1[8] sdc1[9] sdb1[10]
4190208 blocks super 1.2 [7/7] [UUUUUUU]
unused devices: <none>
root@MediaMaster:~#It would appear md127 is still RAID5 - this has already done it's reshaping. It looks like free space did go up by 4TB - which wasn't the intention.
Am I right in saying at the end of this I won't have true RAID6 dual redundancy and md127 would be vulnerable to >1 disk failure??
Is this a bug?? - in my view it really should have converted all the arrays to RAID6.
Looking at mdadm documentation it looks like it should be possible to 'force' md127 to be RAID6 - https://neil.brown.name/blog/20090817000931 - any idea of the specifics?? Will this break XRAID??
I do have a backup but would rather not risk factory resetting.
Thanks
Andy
14 Replies
powellandy1 wrote:
It would appear md127 is still RAID5 - this has already done it's reshaping. It looks like free space did go up by 4TB - which wasn't the intention.
Am I right in saying at the end of this I won't have true RAID6 dual redundancy and md127 would be vulnerable to >1 disk failure??
It looks like it only converted the RAID groups with 6 disks (now 7) to RAID-6, and left md127 - which had 4 disks (now 5) as RAID-5.
That is weird, and I would consider it a bug. It likely is possible to resolve it with ssh - Sandshark has done some experimentation along these lines. Though this is risky, so make sure your backup is up to date first.
I've not done any experiments changing the RAID type of one group of a multiple RAID group configuration. While I'm sure it could be done, the first thing you have to do is turn off XRAID. Otherwise, the OS is going to try and "reclaim" any partitions made free by the SSH commands. And once switched to FlexRAID, this expanded RAID configuration will refuse to go back to XRAID. While it is a lot of work, the only way to have that configuration and XRAID is to back up, factory default, and restore.
While many think XRAID is a proprietary format, it's not. It's "just" a set of logic that determines how to use standard Linux tools (MDADM and BTRFS for OS6, or MDADM, LVM, and EXT for earlier OSes) to expand a RAID volume without operator involvement. I quote "just", because that's not a simple thing. There are a huge number of possible old and new configurations. So, they must have established rules that are intended to handle similar configurations in a similar way. That you ran into a configuration where the logic failed to do what it should is pretty clear, probably because your configuration is a rare one -- maybe even one the programmer(s) didn't anticipate at all.
Thanks.
So what exactly does the XRAID/FlexRAID toggle button in the GUI actually change??
If I was able to convert md127 and all the prequisites of XRAID still existed (which I assume is to do with consistant arrays/partitions etc.. such that it can automatically expand) can it not be toggled back??
Interestingly I had a different problem (https://community.netgear.com/t5/Using-your-ReadyNAS-in-Business/Adding-a-4th-10TB-drive-to-a-XRAID-array-on-Pro6-6-9-3-please/m-p/1614423#M147974) before when it somehow toggled out of XRAID into FlexRAID, but issuing commands via SSH to correct the issue - vertical expansion not triggering automatically - fixed it and upon rebooting it was back in XRAID!
Cheers
A
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