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PostPosted: Wed Jul 03, 2013 5:51 pm 
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Joined: Wed Jul 03, 2013 5:40 pm
Posts: 2
Hi all,

New to the forum and have a peculiar problem I'd like some help with if at all possible.

I was copying a lot of data from a 5big to another volume. After about 15GB the Lacie dropped off and the copy failed. Since then, whenever I power up, I get the blinking large LED on the front and on the back, it goes through each disc (spinning up I presume) and then shows Disc 2 and 5 as red. 1, 3 and 4 are blue.

After about 2 minutes, the blue LED on the front goes solid. After 2 minutes and 5 seconds, the red LEDs on the back go off and so I am left with 1, 3 and 4 that remain blue.

I initially though that I had a couple of drive failures so I powered down and removed Drive 2 from the enclosure, connected it to a PC running Ubuntu Linux and copied the contents of the drive across to a known working drive using 'ddrescue'. I noted that 'ddrescue' didn't give me any read errors.

Anyhow, to cut a long story short, the copy finished and then I inserted the new disc back into Bay 2 and then was going to try and recover some of the data using 'R-Studio'. However, to my surprise, Drive 2 came back on as a red LED and did exactly as the first drive did.

Would I be right in assuming that my enclosure has failed in some way. If this is the case, is there some way of retrieving this data outside of the LaCie enclosure? There is quite a lot of data on it and it's for a client of mine. I understand the importance of backing up after losing all my data a few years back!

Thanks,

Andy


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PostPosted: Fri Jul 05, 2013 7:43 am 
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Joined: Mon Jun 16, 2008 10:45 am
Posts: 6088
How was the raid organized? I suppose raid5 with one parity, right?

The raid manager has some strong constraints on the timing of it's member disks. When a disk doesn't react in time on a command, the disk has to be dropped from the array. The disk could still be healthy, but due to wear it sometimes needs some more time.
Now your array has dropped 2 disks, which means the array is down, as it needs at least 4 disks to run. You have replaced one disk, but unfortunately that doesn't help, because you copied it in it's down status, so it needs to resync. And there is no way to resync, as the parity is down too.

I *think* you should be able to restore the data, as probably only a few sectors of the dropped disk will be out of sync. So if you tell the raid manager to assume the disks are in sync, the internal filesystem might mount just fine. With some luck the damage is in some slack space, or in a system file.

Connect the 4 or 5 disks to a Linux box (sata, e-sata, usb-to-sata, a combination, ...)
Find out the data partition devicenames.
Execute:
Code:
su
mdadm --assemble /dev/md0 /dev/sdb2 /dev/sdc2 /dev/sdd2 /dev/sde2 [/dev/sdf2] --run --force
Of course you'll have to provide your own device names. If that works, mark the array as read-only
Code:
mdadm --readonly /dev/md0
Now try to mount it.
Code:
mkdir /mnt/mountpoint
mount -o ro /dev/md0 /mnt/mountpoint


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PostPosted: Fri Jul 05, 2013 7:52 am 
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Joined: Wed Jul 03, 2013 5:40 pm
Posts: 2
Thanks for your suggestions. I'll give that a go.

Just a quick one, why is the last device in square brackets and if I go down this route and it doesn't work, am I going to trash the array so a data recovery company couldn't retrieve it?


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PostPosted: Fri Jul 05, 2013 8:08 am 
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Joined: Mon Jun 16, 2008 10:45 am
Posts: 6088
Quote:
why is the last device in square brackets
Because I don't know if you connect 4 or 5 disks.
Quote:
if I go down this route and it doesn't work, am I going to trash the array so a data recovery company couldn't retrieve it?
That is not to be expected. Mdadm will or will not be able to assemble the array. In either case it won't touch the 'raid metadata'. You will try to mount the internal volume read-only. So that won't touch the filesystem either.

But you can alway make a typo (or I could have made a typo), or the power supply of your usb-to-sata convertor might blow the disk, or ...
I guess a data recovery company will first create a low level copy of all 5 disks, and won't touch them after that. But I suppose there are also cowboys in that business.


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