I am a bit confused still. Is the 1 and 2 the two parity drives or two of the data drives?
Wouldn't the parity info on the two parity drives be the exact same info? Why would having two copies of the same thing be of any help?
From what I can tell of disParity (maybe I should ask the author, eh?), it appears it knows what is on each drive, that it does not lump them all together. When I run a scan, it tells me the differences for each data drive and then it updates based on that one data drive based on the individual files. When I remove a data drive from the set, it goes through and deletes the parity based on the protected files. Since I have mostly ISO's of BluRays, the files are quite large. This means I can watch it as it runs. It tells me the number of adds, changes, and deletes since the last run, per data drive. When I say to update, it creates the parity info while scanning each file (it lists the file it is currently working upon). When you remove the drive, it does the same thing in reverse.
I will read up more on RAID4 Parity and how it works, it is quite possible I just do not understand.