I have been using a Home NAS product by Dlink (DNS323) for close to 3 years. It is rock solid and serves me well.
But, I keep running out of hard disk space. Initially i had 1TB (500+500). Then I upgraded one of the Disks to 1.5TB to have total 2TB.
And I have run out of space on that too!
So, just upgraded it to have total 3.5TB, by putting in a low power 2TB drive (consumes 50% less power).
The biggest challenge of all was transferring the existing data. DNS323 has no interface to transfer/backup contents between its two drives, though it supports an external USB drive. Had to pull out the drives and connect Hard disks (with EXT2 file systems) to a Linux system to get the job done fast.
Working well so far…