RAID 1 Q&A

Yesterday I offered Prof. Michael Froomkin my services as a Windows adviser. Today, he takes me up on the offer with this question:

I’m never one to pass up the chance of free advice from a real expert. So, Ed, here’s a question that’s bugging me:

My home computer runs WinXP, with RAID 1 provided via the ASUS motherboard [for the non-techies, RAID 1 is when your hard disk is mirrored by another identical hard disk]. The machine came from the suppliers with XP on one huge partition, and I’d like to repartition my hard drive(s) into several smaller
partitions — not necessarily all for Windows — without losing any data.

I had thought to use partition magic to do the job, but apparently Partition Magic 8.x doesn’t’ support RAID 1.

Can it be done? How about if I

1. 1. Turn off RAID mirroring.</li
2. Use Partition Magic or something else like it.
3. Start RAID mirroring from scratch (will it catch all the partitions? will it faithfully copy all the changes to each one?).

I did a Google search, and all I know now is that I’m not the only one who wants the answer to this one…

That’s exactly how I would do it. Caveat: I don’t currently have a computer in my lab here with drive mirroring enabled on it, so I can’t physically test these steps. But the procedure is fairly straightforward.

First, note that the article you reference is referring to RAID volumes created using the software tools in Windows NT/2000/XP. It’s possible (but hardly guaranteed) that Partition Magic will recognize your hardware RAID volume. Have you tried?

Hardware RAID solutions work by creating the illusion that your two physical drives are a single unit. The array is managed by the hardware controller. You need software drivers in whatever operating systems you plan to use so that the operating system can work with the RAID array you create. As far as Windows is concerned, you have a single drive; the hardware hides the individual members of the array completely. (The same is true for other operating systems.) After you load the correct driver, you can partition the drives however you want.

The first step, of course, is to make sure you’ve got a really great backup, just in case something goes wrong.

Your hardware controller should allow you to break the RAID mirroring. Doing so should leave the data on the first drive intact. If so, then you’re good to go. Re-partition that disk as you please, using Partition Magic to shrink the main partition and create new ones from free space. Then create a new array. If you’re using a Highpoint controller, choose the Duplication option to copy the data on the source disk to the mirror disk. The hardware RAID controller doesn’t care what’s on the disk; its job is to mirror the content from one disk to the other for reliability’s sake, and it works at a very low level, independent of operating systems. All of your partition information should be intact. When you view it from an operating system that has the correct drivers, it looks like a single disk, which you can manage using whatever partitioning tools you like.

Personally, I’m not a big fan of hardware RAID. I would rather use that second drive as a backup device, using Norton Ghost or a similar disk-imaging program to keep compressed copies of each partition on the main drive. If you have a problem with the original drive, you can restore a backup of one or more saved partitions easily. You don’t have to mess with low-level utilities, and you have more flexibility, including the option to save your backed-up images to another medium (such as writable CDs or DVDs) for offsite storage.