Quick question about mirroring: Please help, server is down!

Posted on 2004-08-27
Last Modified: 2010-04-14
I have a machine that has a Promise IDE controller in it as a separate card. I have two 40 gig IDE drives that are mirrored in this machine. Well I think the controller card has crapped out because the machine won't boot unless I take the card out. I need to get this machine up and running as soon as possible, so this is my question.

1) Can I go out and buy a new IDE controller card and plug these drives in as if nothing ever happened? Or is the mirror setup embedded onto that card?

2) If worse came to worse, could I just plug the two drives into the onboard IDE controllers? If I do this, will Windows continue to act as if they are a mirrored set of drives?
Question by:Gabe_Rivera
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Expert Comment

ID: 11918350
You should be able to buy another IDNETICAL

Expert Comment

ID: 11918362
Sorry about the previous comment, slip of the touchpad...

You should be able to buy another IDENTICAL card, setup the mirror, and be good to go.  I would double check the documentation, or make a quick call to the manufacturer just to be 100%.

LVL 95

Accepted Solution

Lee W, MVP earned 500 total points
ID: 11918763
You don't mention if it is hardware Mirror or Software mirror.   However, this shouldn't really matter, only how you restore the mirror will be different.

If it's hardware mirroring - the promise controller's BIOS supports mirroring and in the BIOS you have told it to mirror the drives, then Windows has NO CLUE it is being mirrored.  This means you can take EITHER drive and plug it in to a new controller (or the onboard controller), and boot it, though you will PROBABLY have to modify the ARC path (especially if you just switch to the onboard controllers).

If it's software mirroring and BOTH drives were working off the promise card, then the mirror is all but certainly created using Windows dynamic disks and built in Windows Mirroring.  If this is the case, then you should be able to reconnect EITHER drive to a new controller and like a hardware mirror, with the probably requirement of editing the ARC path, you can boot the drive.

For the moment, regardless of the type of mirroring, consider the mirror broken - this just means you have 2 drives with the identical OS setup that can boot up independently.  You will have to RESTORE the mirror.

If this was a hardware mirror, then get a new mirror capable (RAID 1) controller card, connect both drives, and when you boot, go into the controller's BIOS and reconfigure the mirror  (if you want to be safe, given the cost of IDE drives nowadays, buy another drive as well and instead of putting both original drives on the new controller, put one of the original drives and the new drive in the system and mirror onto the new drive.  This way, if something did go horribly wrong, you have the other half of the mirror to continue trying to recover from.

If this was a software mirror, then plug both drives into the system so they are recognized.  You may need to reconfigure BIOS to tell it where to boot from, but get it booting from one of the drives.  Windows will report the mirror is broken and you'll have to regenerate it.  This slows performance for a time, but nothing is lost.  As above, to be safe, you might want to use a new drive instead of putting both halves of the mirrors in the system.

Now, as I mentioned earlier, you may need to modify the ARC path.  For detailed instructions on what the ARC path is and a better understanding of the values you may need to change, depending on your config, please see the following MS KB article.

In short, the ARC path is in the BOOT.INI file and defines the location of the Windows NT/2K/2K3/XP installation.  It specifies the controller, lun, disk, and partition where the Windows installation can be found.  If you swap controllers the ARC path may change.  If you have/boot to a 2K3 and possibly XP recovery console, there is a command that will more clearly state where the windows installation is, in terms of an ARC path.  (Or so I believe - I only did that once - I think the command was either MAP or DISKPART).

Note: Software mirrors are not dynamic - meaning that if a disk fails that is being mirrored through Windows software, the system will crash.  You will then need to tell it to boot off the functioning disk.  If the disk fails on a controller that supports hardware mirroring, then it SHOULD be seemless - the server should continue to function with no known (to the user) problems with performance or availability.

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