First, the technique:
- Swap in your new drive.
- Let it rebuild.
- Swap in the second drive.
- Before it gets done rebuilding, use the "delete disk" option:
- Restart the unit
So why would anyone ever want to go smaller with one of these units? Well, suppose you had a pair of SSD drives that you picked up for cheap from Woot! or some other retailer. And suppose you picked up a pair of Icy Dock 2.5"-to-3.5" HDD Converters so that they'd fit correctly in the drive frame for the ix2? Well, you would then have the opportunity to create a smoking fast NAS with those SSDs.
I don't know enough about the StorCenter's Linux kernel (or Linux kernels in general) to tell if the unit can or does use TRIM to keep the write speeds optimal. But let's be fair: even without it an SSD blows away spinning disk at any speed. Given the cost/capacity ratio of SSDs, however, you'd have to be pretty starved for performance to try such a thing—and would certainly be better served by putting SSDs in a higher performance box than an ix2-200!