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Accessibility of RAID-1 array member

Posted on 2008-10-14
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Last Modified: 2013-11-09
Hello to All,

Preamble:
 Months ago i created a RAID-1 array using Intel's ICH9R SATA-RAID controller embedded in my Gigabyte motherboard running WinXP Pro.

History:
 The system worked fine for months until yesterday when the user experienced a hang and boot errors he tried to fix with CHKDSK... which he interrupted :( when he found it took too long!
I found the BIOS SATA RAID/AHCI mode setting to AHCI which gives me a hint he may have tampered with the setting as well! :(
The boot-time RAID configuration utility reported the array state as: VERIFY which i have never seen before and do not know what it means.
Now, WinXP has been caught in an endless boot-reboot loop. If I change the BIOS setting to RAID (which i believe is the correct one) WinXP displays immediately about the disk configuration not being correct and does not try to boot at all!
When i try to boot WinXP CD using F6 to supply the driver it recognized the disk but it says that it can not enumerate directory contents on C:, on the boot-time RAID utility the status now was Failed indicating that the second disk has failed. I tried to swap the disk with a new identical one but i was not able to get it to rebuild the array!

Problem:
I am more interested in getting access to the data than making XP boot again!
(Not that making it boot again with everything on it OK, would make me unhappy :)
Being it a RAID-1 array i expect to be able to simply attach any surviving RAID-1 member drive to another system and it should be visible!
But when I attach ANY of the two disks on a working plain SATA WinXP machine, Disk Manager can not recognize anything on the drive - except that it has a partition (does not report the filefystem) on it and that it is healthy.

Questions (please answer quoting authoritative URL):
1) Can a RAID-1 array (created with this specific controller) member disk be accessed by another plain SATA controller or is it that the RAID controller has created proprietary structures that make the drive appear scrambled to a plain SATA conhtroller?
2) How can one instruct this controller to rebuild the array after a failed member is replaced?

Thank you,
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Question by:xchange
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2 Comments
 
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Accepted Solution

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cuziyq earned 500 total points
ID: 22713259
The problem with ICHx integrated RAID controllers is that A) they DO use proprietary structures to manage the array internally, and B) they do it in a half-assed way that still would allow an operating system to "see" an independent array member as an individual disk, but not work properly with it (the LBA mappings are slightly off).

What probably happened is this:  The RAID functionality was turned off so that the controller was set to normal SATA.  Normally, this wouldn't be a problem, as the driver would load and straighten it out from within Windows.

However, the user probably ran CHKDSK from an XP CD or some other medium that did not have the Intel ICHx drivers on it.  It saw the disks as two independent drives, tried to "fix" one of them, and now the two disks are no longer identical.  When you boot XP with the controller configured as normal SATA, the RAID driver loads, sees the disks in the array, tries to do its magic, but fails.  This is why the array says VERIFY on it (the driver has no idea which disk is the "good" one).

In a normal RAID-1, the controller sends read requests to both drives in the mirror and accepts the first one to respond while ignoring the second.  But since they're now slightly different (but mostly the same), read requests coming from one drive do not line up when a read request gets accepted from the other drive, and that causes XP to puke.

Here's what to do:

Set the controller to normal SATA mode, then boot from a BartPE disk (you can make yourself one on another machine using PE Builder at http://www.nu2.nu/pebuilder).  Both C: and D: should have an identical set of files on them.  Copy your data off the D: drive to a safe location.  DO NOT WRITE ANYTHING TO D:!

Once that's done, set the controller back to RAID and then reformat/reload the system restoring your data.  That should take care of it.

Let me know if that works.
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by:xchange
ID: 22808769
cuziyq, thank you for the quick reply.
I presume your instructions to "Set the controller to normal SATA mode, then boot from a BartPE disk and copy my data off the D: drive to a safe location." imply that the disks' contents should be visible from a different working XP box if I attach the disks to it, but they are not - as I stated in my question.
Why should the disks be visible from Bart's CD? It would not have the drivers too! (In your instructions you do not say anything about it).
 Yet you gave me hope. Because I was in a hurry, I used OnTrack's commecial product and it extracted my data off one of the disks (the other was probably the failed member).
 So, it seems (to me) that  the individual member WOULD be visible from another XP box or Bart's CD, IF its's directory structures were not messed-up (something that the recovery program was able to deal with).

Thanks again,
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