# mdadm raid10 recovery [SOLVED]

## rada

Hi everyone. I've been running a raid10 array with 3/4 drives for a little while now and my newest drive (08/2009) started making some weird noises, not accesible. I restart my computer and the drive works fine. I started a smartctl -t long for the drive. Now the problem is the md superblock of the other two drives in the array. They say this third drive was 'failed removed'. The drive in question lists all three devices.

The problem is the 2/4 raid10 drives left cannot boot the array. The 'failed removed' needs to be changed to 'active' with all of the drive's info back in the superblock, alas this is impossible since the array cannot be booted. I already lost a 100GB raid5 array by zeroing the superblock and recreating a new array with the wrong chunk size. Something tells me some similar --zero-superblock trickery must be done to this array to fix it again. Does anyone have a solution? I really don't want to lose this 1.6TB array I've been building for the last few years.

Thanks, -RadaLast edited by rada on Wed Aug 31, 2011 8:07 am; edited 1 time in total

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## paziu

you are asking to give you an advise on "LIVE" data, my advise is not going to solve your problem, but prevent from loosing whatever you got left. spend some money, do a block2block copy using dd or parted magic of all drives you got there, mark each drive with a pen, replace them and work ONLY on the mirrored/copied configuration - there might be several solutions, of which only a few might work, or just one may be the ultimate choice. never do any "experiments" on LIVE data unless you have a backup that meets your satisfaction OR you are ie. sure that you can force a failed disk to "on-line" state on a >degraded< config ( do not do it unless you are sure )... by rewriting the signature or simply 'online'ing' a disk that its live span ends....( often using a hammer worked also - talkin about 515MB 'enterprise' disks used in '90s - hda was 90 pounds without the 'logic' and its enclosure... just hda, the true HDA [assembly not adapter] - but this is a different topic...)

RAID is only as good its failure recovery options - very often requires very good knowledge of the features, and a good decision based on its state - often the decision is not documented or explained in the "user's manual".....

this is what you going to hear from me, probably what you do not expect from this forum.... I hope there will be an "ultimate choice" post next after mine.... good luck rada

ps: i have never been a 'fan' of any king of software/OS based (so called) "raid solutions", think about getting a good LSI/AMI controller for your data... very portable, independent from the hardware/chipset/whatever - just >>cool magic<<.

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## Mad Merlin

So you had a 4 drive array with 1 bad disk running for awhile, and eventually a 2nd drive failed in the array, leaving you with only 2 drives (which is often not enough to start the array, depending on your luck), and now you can't assemble the array anymore?

There's a force command for add, something like so:

```
mdadm /dev/md0 -f -a /dev/sda1
```

Which should allow you to add the most recently failed drive back into the array, albeit with some blocks out of sync with the rest of the disks. At this point, you should back up all your data and replace the two failed disks.

I wouldn't fiddle with the superblock directly, too easy to make mistakes.

 *paziu wrote:*   

> ps: i have never been a 'fan' of any king of software/OS based (so called) "raid solutions", think about getting a good LSI/AMI controller for your data... very portable, independent from the hardware/chipset/whatever - just >>cool magic<<.

 

Not independent from the raid card! When it goes up in smoke, so does your data.

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## rada

Turns out the hard drive was dead and I lost all the data after all. Thanks for the info though, definitely would work with good hardware.

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