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HDD Failed in a RAID Array

Posted on 2014-02-16
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Last Modified: 2014-02-23
Our server PowerEdge 2800 restarted due to a power failure.

There was 2 Raid arrays. One for OS and one for Data.

Now there is one array(OS array) healthy and other array (Data array) one hdd failed.

I opened disk management I saw disk is not initialized.

How to get the data, EE expert's quick response is highly appreciated.
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Question by:-MAS
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Expert Comment

by:Mandeep Khalsa
ID: 39863685
What type of RAID are you using on the data array? Have you replaced the bad disk with a new one?
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by:-MAS
ID: 39863706
First of thanks for your quick response
I could not see the size of hdd so I could not understand what array is configured
no.
We dont have a spare HDD to try
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by:samjomoore
ID: 39863725
The first thing that I would do is find out what type of RAID you have.  Make sure you understand RAID levels here: http://www.thegeekstuff.com/2010/08/raid-levels-tutorial/

Next, I would boot into the RAID controller BIOS (watch the boot messages as they come up and press the correct key when asked to do so) and see if the configuration of that array is still stored properly.  If it is just the configuration of the array that got lost due to the power failure, you may be able to reconfigure it the same way it was without initializing the disks.

Beyond that, the controller should tell you if one or more of the HDDs of the array have failed, and it will tell you which  one.  If so, you need to get a new HDD (same size as the old one) and replace the failed one.  Then you can rebuild the array.  There are commands to do all this in the controller's BIOS.

If more than one disk failed, I hope you have a backup.

Lastly, if the controller failed, you will need to replace it, and reconfigure your arrays the same way they were with the original one.
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by:-MAS
ID: 39863736
I checked the raid configuration utility and I found 1 hdd failed. Do you think I can replace n rebuild the raid?
Appreciated your help
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by:samjomoore
ID: 39863741
Yes, I believe you can.  What I would do is get 2 new HDDs.  First get one of them and create a hot spare with it.  Once it is ready I would replace the failed HDD with it.  The controller should convert the hot spare into the replacement.  After that, I would get the other new HDD and make it a new hot spare and leave it there, just in case this happens again.
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by:-MAS
ID: 39863861
"PS2 AC lost
PS Redundancy lost        
Ovrflw check log"
This message is diplaying in the screen
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Expert Comment

by:Mandeep Khalsa
ID: 39863864
What is your RAID? 0, 1, 5, 10, 50?
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by:-MAS
ID: 39863960
C drice RAID1  (OS)
D drive RAID0 (DB)
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Assisted Solution

by:samjomoore
samjomoore earned 125 total points
ID: 39863973
If you checked your RAID levels, you already know what this means.  This says that your OS is RAID 1, which is a mirrored drive.  This means that there are two HDDs mirroring each other.  If one fails the other one continues to work,

It also says that your DB (I assume it is your database) drive is RAID 0, which means that this is a single hard disk with no mirror.  If this drive fails your data is gone.  From what you said at the beginning, this one seems to be the one that failed.

To recover your data, I hope you have a backup.  You would need to install a new array, and I would make it RAID 1 at least (to have a mirror).  

If you don't have a backup, then you might need to send in your failed disk to a recovery service to see if they can extract some of the data out of it, while you rebuild a new array to store the recovered data.
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by:-MAS
ID: 39863982
C drice RAID1  (OS)
2x146GB

D drive RAID0 (DB)
2x360GB

is it possible to get the data if I configure a new HDD as hotspare in the current RAID0 Array?

If not what is the next possible way to get the data before going for a HDD recovery
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Expert Comment

by:samjomoore
ID: 39864024
This is not making sense.  RAID 0 means "no mirroring".  I see that you say you have 2 x 360GB drives, but this RAID configuration does not allow for data recovery that way.  A hot spare will not help you without the ability to reconstruct the data that is supposed to be there, and RAID 0 does not provide that ability.

The next possible solution would be to restore your backup.  If that doesn't work, then I would seek a HDD recovery service.
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Author Comment

by:-MAS
ID: 39864028
Ok
Is it possible to get the data from the 1st HDD in the RAID0?
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Assisted Solution

by:Mandeep Khalsa
Mandeep Khalsa earned 125 total points
ID: 39864032
RAID 0 is striped, meaning half the data is written on one drive and the other half on the second drive. So no you cannot recover part of the data.
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Expert Comment

by:Surrano
ID: 39864185
To explain in more detail, striping means that the disks inside the stripe are addressed in a round-robin fashion. It's not like "first 360GB is on disk1, second  360GB is on disk2, etc". It's like "128k on disk1, 128k on disk2, ... 128k on disk{n}, then start over" (stripe size may differ from 128k). So it's very unlikely that you'd be able to fully recover even a single file that is larger than the stripe size (and may fail even if it's smaller than the stripe size)
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Assisted Solution

by:Gerald Connolly
Gerald Connolly earned 250 total points
ID: 39864213
AS the others have said RAID-0 has no redundancy and therefore if you lose one of the members of the RAIDset your data is toast and not easily recoverable.

Your only options to recover your data is
1) From your backups - You do have backups i hope.
2) Commercial data recovery company - but this is unlikely to be cheap.
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Expert Comment

by:SelfGovern
ID: 39864737
And for others reading this thread -- do the math: RAID 0 means that if you have two disks, you're doubling the chance of a catastrophic failure.  If you have three disks in RAID 0, you're tripling the chance of catastrophic failure -- and so on: because if ANY disk fails, you lose ALL your data.  

RAID 0 may get you a tiny bit faster data access -- but you'll typically never notice it in real life.   It's like trying to get where you're going when driving faster by not fastening your seat belt first.  You'll never notice the difference -- until the crash.  And then you (or your data) may not be alive.

Other levels of RAID have some level of redundancy built in -- you can lose a disk and still have your data.  But DON'T use RAID 0 unless it's for strictly temporary data that you can reconstruct if a disk fails.
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Expert Comment

by:pgm554
ID: 39866358
What the raid controller?
When it boots,it should give you a model number.
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Author Comment

by:-MAS
ID: 39866546
I am not sure of the model number.
I am not at site now
But it was Perc.xxxxxx I guess

I will give the correct details when I visit the site
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Accepted Solution

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Gerald Connolly earned 250 total points
ID: 39866762
Just remember if you do go to commercial recovery, the more DIY recovery attempts, the less  chances that the commercial company can recover your data
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Author Comment

by:-MAS
ID: 39866949
You are right now both the HDD status showing "Failed"

Do you think now it is worth giving to a company for recovery as even if the data is not recovered there will be service charge for their attempts.

Your advice is appreciated.
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Expert Comment

by:Gerald Connolly
ID: 39867128
Some companies will charge to assess what can be recovered and some do not. but all will charge to actually deliver the recovered data.
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Author Closing Comment

by:-MAS
ID: 39881669
I recovered from a local recovery company.
but it was little bit expensive but its worth paying that money for that data.
Thanks to all
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