It's been a while since I created these logical volumes and extended my volume group (the only one) to include the newly grown raid5 array on a 2-2-1 TB device. Frown all you want as long as it works. When that 1 TB HDD shows some signs of failing or error, I'll replace it with a 2TB HDD. The raid array will then be a complete 2-2-2 TB raid5.
Here's the status of the raid array now:
I'm replacing the 1 TB HDD when it fails or errors, or when I need to increase the capacity of the array, whichever comes first. The present raid array size is 2 TB.