Well, just out of curiosity, let's look at a different possibility...
The raid will operate in degraded mode with a drive missing. I think I remember reading that the n2100 is a software raid. That being the case, is it possible that the drive could be mounted via a usb enclosure by another OS (Mac/Ubuntu, etc.) which has support for ext2 or ext3?
The Drive Utility with Mac os is capable of creating raids and altering partitions, so could it mount a raid created on another linux box? And then increase the partition?
I don't know how much time/effort this would save... I guess it would resize the partition without having to copy/recopy, then rebuild. So that would be a start.
I found this page via google thus my posting here.
What i did for my raid 5 which sounds like we have a similar problem, is i changed all the drives out - 500gbs for 250gbs. However the raid was still at 750gb (3x250, 1 for parity). So to increase the raid size i used: "mdadm /dev/md0 --grow--size=max"
now the array is reported as 1.5Tb. "mdadm --misc -D /dev/md0"
however the underlying partition of fs (not sure which) is still at 750gb.
I created a test machine on a virtual version of fedora and tested out my theory before trying.
So my next step is to e2fsck -f /dev/md0 o check the array. once completed i need to umount the array then do a "resize2fs /dev/md0"
however i cant unmount the array. I get "invalid argument". all the commands on the theucs are sym links to busy box. It has been reported as a bug, as noted above and on their site.
So i have no where to go from here presently until i can get the array unmounted. Just thought i would share what i have learned to date.