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How do I boot to one drive of a RAID 1 array

Posted on 2011-03-06
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Last Modified: 2012-06-27
I have a perc 4e/di raid controller with a mirrored first array.  One disk failed in this array and also fails a rebuild.  I do not have a replacement disk right now but would like to boot to the one drive that is left.  Do I have to "break" the mirror before I do this?  I don't see any option for that.
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Question by:tjwill
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by:hunart
ID: 35046222
If you mirror is still intact, replace the defective drive with the same drive, the mirror will rebuild itself.  Can you load the OS normally?
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by:dlethe
ID: 35046226
Just make the surviving disk the primary boot device. Do NOT muck with the RAID config.  You want it to stay in a degraded mode, so when you do get a spare, the RAID will get rebuilt properly.
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by:andyalder
ID: 35046227
It should boot off the remaining drive without intervention, doesn't it boot for you? You may need to press F1 or something to let it boot with the array degraded.
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by:tjwill
ID: 35046277
I only get to the ctrl-m portion of the boot up.   It won't go past that.
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by:tjwill
ID: 35046284
I have done nothing with the RAID config out of fear!  I've only gone into the controller bios and tried to rebuild the failed drive.  I don't know where to go tell it to boot to the surviving drive and it seems I need to give it some instruction...  I just can't find where to do that.
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by:dlethe
ID: 35046404
Please be specific when you say it fails a rebuild.  Does that mean you put in a known-good replacement drive (i.e, just swapped out the bad for what you thought was good?)
There will be some additional information.  

-> If it "fails" a rebuild, you have generally 2 possibilities.  The replacement drive is no good (so get a replacement replacemnt)
-> or, it gets an unrecoverable READ error on the disk that did not fail, so it gives up.  If that is the case, then you can repair this, but it will be painful. (Use a linux machine to force a write on the unrecoverable block, and you need a non-RAID controller).

Or is it something else.
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by:hunart
ID: 35046405
Have you made any changes inside the RAID Configuration?  Technically, when one drive fails, the second drive will continue work.  Do you have a working hard drive which you can replace the defunct drive?  If you do, put it inside the drive so the system can rebuild the RAID itself?
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by:tjwill
ID: 35046432
I do not have a good spare drive right now.  I just want to boot to the existing drive.  I'm not worried about rebuilding the RAID at this moment.  I just need to boot the system from the remaining drive but I cannot find anything that lets me point to that as the bootable drive.
Is that the only way a mirror works?  You have to replace the bad drive so it can rebuild?   I assumed it will boot from the one good drive if the first drive fails.  It is not doing that.
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by:andyalder
ID: 35046450
Looks like there's no option to let it boot from a degraded array in BIOS setup, http://www.cs.uwaterloo.ca/~brecht/servers/docs/PowerEdge-2600/en/Perc4di/UG/bios.htm#1112378 (sorry not link from Dell's site but Google is giving silly results at the moment). Pity it got powered off before you got the replacement.
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by:tjwill
ID: 35046511
Well, that's exactly what happened.  It was running and I turned it off.   I can't imagine that is the end though!   Are you deriving my misfortune from the perc manual?
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by:andyalder
ID: 35046663
I think "no action is taken by the BIOS" means it doesn't boot the remaining disk - see http://support.dell.com/support/edocs/storage/raid/perc4e/en/ug/chap6.htm#1054194

I would assume you got a "x Logical Drives Degraded" message on boot and not a BIOS is disabled message.
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by:tjwill
ID: 35046851
That looks like I can rebuild if I can get another drive in there.  Since I dont have one, I was hoping to boot from the last one.  Maybe I'll try to get another drive..   (Sunday morning ??)    
Yes I did get "Logical Drive Degraded" message.  
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by:PowerEdgeTech
ID: 35046923
As  has been stated, there should have been nothing for you to do to boot to the other drive - IF the other drive is ok and your array is still functioning.  No settings to change ... just a message that the array is degraded (or failed, if it is not working).  If you go to CTRL-M, Configure, View/Add, what do you see (if asked Disk View or NVRAM View, choose Disk)?
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by:tjwill
ID: 35047131
I don't get a Disk or NVRAM View designation.   I just get an array selection menu.
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by:PowerEdgeTech
ID: 35047144
Ok ... and what drives and status is listed there?  
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by:tjwill
ID: 35047148
If I press F3 for Logical Drive info,   I get
LD:0   RAID:1  #STRIPES:2  DRIVE STATE: DEGRADED
LD:1   RAID: 5 #STRIPES:3  DRIVE STATE: OPTIMAL
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by:tjwill
ID: 35047154
Also for RAID channel-0   I get  
ID 0  FAIL   A00-00
ID 1  ONLINE  A00-01
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by:PowerEdgeTech
ID: 35047160
At any point, did you get a message in BIOS/POST about a Mismatch?  If so, what did you choose?
What message are you getting when you try to let it boot to Windows?
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by:tjwill
ID: 35047171
I don't get a mismatch message and it never gets past the configuration utility.  It just tells me to reboot and pauses at the ctrl-m point again.
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by:tjwill
ID: 35047181
This last time that I rebooted ..  it asked me to press any other key to continue.  It didn't ask me that before.  It is now for the first time trying to load windows.
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by:PowerEdgeTech
ID: 35047195
You would have only gotten the Mismatch message once, and if the wrong choice was selected (or no selection made at all), then it may have imported the incorrect RAID configuration.

Can you tell me the exact wording of the part that "tells [you] to reboot"?

You might consider calling Tech Support (800.822.8965) - support is always free regardless of warranty status.  It would be much easier to walk through the options and possible next steps on the phone.
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PowerEdgeTech earned 250 total points
ID: 35047198
Well, that's promising.
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by:tjwill
ID: 35047231
I have to say that you went step by step with me a little bit.   I can't say necessarily that you fixed anything but you certainly made me slow down and look and not do anything stupid.   I didn't have to go out and buy another drive today.    I am now going to make sure everything is backed up.   I have to award you the points for taking the time.  THANK YOU!
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by:PowerEdgeTech
ID: 35047252
Not sure I did anything either.  Typically, if there is a mismatch between what the controller thinks and what the drive(s) think, the only way to resolve the mismatch is to go into CTRL-M, Configure, View/Add.  You didn't see what I would have expected you to see, but perhaps it helped resolve any question the controller had, nonetheless.

Either way, glad it's back up.
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