Author Topic: Mdadm RAID assembly query  (Read 756 times)

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Offline doac00

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Mdadm RAID assembly query
« on: January 14, 2020, 12:22:45 pm »
Folks - I have a NETGEAR NAS with RAID5 that had a disk failure so I inserted a new disk, it was mostly through recovery when another disk failed (WD NAS HDD's) - thus the RAID will now not assemble. I do not want to try a forced assemble as I'm not competent on Linux hence asking for expert advice.

I have checked the integrity of the disks with the WD utility by connecting them to my PC- and all is okay

I'm fairly certain the event count on 3 of the disks are very close (if not all the same) apart form the one on the initial failed disk so I'm hoping that as the disks (apart from the actual failed unit) are all good that I may be able to re-assemble and recover

Right now I solicit your advice on what would be the best path forward - what information would be needed to try and do the re-assemble??

Offline Gil

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Re: Mdadm RAID assembly query
« Reply #1 on: January 19, 2020, 02:04:32 am »
I had what appears to be a similar problem with a Omnius NAS. It got very warm with all the disk access causing it, I assume, to shutdown. I shut it down for a day and started it up with external fans on it, at that point I was able to get the data recovered. I hope this helps.

Offline Mad Penguin

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Re: Mdadm RAID assembly query
« Reply #2 on: January 26, 2020, 07:05:34 pm »
Mmm, typically if you lose 2 disks on a RAID5 you're out of luck. The fact that the replacement was "nearly" finished doesn't necessarily get you that far as it will be incomplete, i.e. there will likely have been "some" unique data on the second failed drive that won't have made it to the new drive .. whereas a forced assemble "might" work, it would (imho) be "pot luck". The trick with these things is to replace the disks when they start to show signs of wear, typically by looking at the SMART output. Once you get a complete failure on one drive then unfortunately, you're sort of playing with fire, especially if all the disks are the same age ... assuming you don't have backups (?), you could try a specialised data recovery company, but this would likely be very expensive and come with no guarantees. (it is possible, for example, depending on the fault, that they could fix the drive enough to complete the resync)

 


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