As soon as RAID controllers started being built into affordable motherboards, I decided using RAID for my home PC was a good idea.  For the last 6-7 years, I have used RAID on every PC I have built.

There are several RAID configurations.  RAID 0 (striping) utilises two or more identical hard drives, and splits each file equally across them, yielding much faster disk performance (limited by the throughput of the disk I/O controller) as the disks read and write at the same time.  The total available storage is the sum of the individual drives’ capacity.  RAID 1 (mirrored) could be considered the opposite of striping, in that each file is written to all disks.  This effectively provides realtime backup since the content of all drives in the array is identical, with no performance cost.

I’ve only ever used RAID 0.  For a home PC, RAID 1 doesn’t offer any real benefits that cannot be achieved with a half-decent backup policy, but effectively doubles the cost of disk space if you use two disks.

The only down-side to RAID that I had found was that drivers need to be provided during the installation of Windows.  Linux is slightly better in this respect because it has native drivers for the most popular RAID controllers, usually providing basic functionality.  Windows, however, asks that you provide the drivers on installation, presumably so that you benefit from all the features that the RAID controller offers.  With Windows XP you were required to hit F6 during the installation, and provide the drivers on a floppy disk (which was a real pain, since floppy drive usage died out shortly after the discovery of fire, and RAID drivers often came on a CD anyway).  With Vista and Windows 7 the installer is slightly more intelligent.  It will recognise the presence of a RAID array, but it will still require drivers to be provided.

This is all fine; once you’re familiar with the quirks of the Windows installer it’s plain sailing.

But RAID 0 has its own special drawback, especially when you’re not expecting it.  If you take a disk from an old RAID 0 array, install it as the main disk in a PC and try to install Windows 7, you’ll have a nasty surprise.  Usually the Windows installer will acknowledge the presence of a drive, even if it can’t do anything with it.  But not with an ex-mirrorred array disk.  The Windows installer doesn’t even recognise the disk as being present.

Presumably this is related to the fact that the RAID controller had written its own form of partition information to the disk; while the Windows installer can partition and format a raw disk, or one that is already partitioned, it cannot do anything with a disk whose partition information is present but apparently corrupt.

And the icing on the cake?  You can’t repartition the disk without it being partitioned..!