To upgrade the OS, I need to do a clean install. As the raid array is set up in BIOS and appears to the OS as a single drive, my guess is that I can wipe the OS drive and do a fresh install with no harm to my RAID array. Essentially, it will be right there waiting for me when the install is complete. Is that, in fact, the case?
I seem to remember installing a driver for the RAID array when I first set the computer up, where is that driver stored? Would wiping the OS drive kill that driver and the RAID drive in the process?
I, of course, anticipate the totally reasonable suggestion, "make a backup dumb-ass," but, unfortunately, I don't have anything else that can store 4 TB of data. If the array crashes, I do have the media on the original DVDs and BDs, but re-ripping all my stuff would be a royal pain. As data security is all about reducing risk to an acceptable level, I guess I am looking for the odds of failure. If the odds of killing my array are high enough, it may be worth my investing in 2 2TB drives, as opposed to living with the risk that I may have to spend time re-ripping discs.
One other question, if things go sour, how likely is it that reinstalling a pre-upgrade image of the OS drive would sort things out?
You are correct in saying that it will not destroy your RAID 5 array. Just use the partition you used to boot Vista from and do a clean install there. I'm not sure if the Windows 7 installer disk can read GPT partitions though. Might have been better to set one partition up as MBR and the rest for GPT.
OH, you have a separate drive for the OS? That makes it even better. The Windows installation will not mess with the RAID array in any way. It will only touch the OS drive. As for the drivers you are talking about, they are there so that Windows can properly recognize the RAID 5 array as a drive. It has nothing to do with what's in those drives, only how the OS communicates with it.