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#1 2018-10-07 15:59:44

mjellis1687
Member
Registered: 2018-02-05
Posts: 7

[Solved] Bringing dmraid Back Online Safely

I have a software RAID 1 configured with two drives using dmraid. The volume has two partitions. Several months ago the RAID stopped working and the drives began to act independently meaning at boot, there was a 50/50 shot that one of the two drives would be mounted for each partition. I continued to use the partitions without knowledge that the drives were no longer mirroring each other creating a situation where the contents of each drive diverged. I later realized what was going on, but did not have a chance to fix it. I began manually mounting the specific drive that I considered to have the up-to-date partition. After an update this past week, my dmraid began working (my mistake - I should have stopped the dmraid). I ripped out one of the drives in fear that the RAID would start to reconstruct itself and then, delete my files.

My questions are:

1. What will happen when I plug in the second drive? Will the software RAID be "smart" enough to tell which file is the latest version? What about file version conflicts?
2. If it is not smart enough to handle file versioning, what is the best way to fix the drive contents and bring my volume back on-line with both drives?
3. Are there any other suggestions about this situation that I should know about (I have already made complete back-ups of both drives, but I am trying to minimize the amount of work involved in fixing this)?

Many thanks in advance!

Last edited by mjellis1687 (2018-10-10 00:06:21)

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#2 2018-10-07 17:07:42

loqs
Member
Registered: 2014-03-06
Posts: 17,197

Re: [Solved] Bringing dmraid Back Online Safely

mjellis1687 wrote:

1. What will happen when I plug in the second drive? Will the software RAID be "smart" enough to tell which file is the latest version? What about file version conflicts?

Depends if the array has a Write-intent_bitmap.

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#3 2018-10-09 01:31:06

mjellis1687
Member
Registered: 2018-02-05
Posts: 7

Re: [Solved] Bringing dmraid Back Online Safely

I am using dmraid and cannot tell if the array has a write-intent_bitmap or not. Although after more digging, it seems like my best course of action is to simply start from scratch...

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#4 2018-10-09 09:35:21

loqs
Member
Registered: 2014-03-06
Posts: 17,197

Re: [Solved] Bringing dmraid Back Online Safely

If you are going to start again unless you need to share the array with another none Linux OS I would suggest switching from fakeRAID to software RAID.

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#5 2018-10-10 00:06:05

mjellis1687
Member
Registered: 2018-02-05
Posts: 7

Re: [Solved] Bringing dmraid Back Online Safely

@loqs: Thanks for the link and suggestion. I will mark this thread as closed as I do not believe there is an "easy button" on this quickly getting back my old array without risking data loss.

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