Expansion - 8 & 16TB?

zamboni wrote:
The array cannot expand beyond 16 TB without a factory reset (and full data restore). >> Why cannot a small tool be created that systematically moves data and recreates sectors - even if it takes a week? Backing up 12-ish TB to temp space while having 16+ TB in your array is absurd.

That "small tool" is already in the ReadyNAS; it's what does the automatic expansion when you increase the size of a drive. It doesn't work with >16TiB arrays because it was written under the assumption that the number of sectors in the array can be expressed in a 32-bit number, but 4 billion is the largest number that can be expressed in 32 bits (1111 1111 1111 1111 1111 1111 1111 1111 unsigned binary = 4,294,967,296 decimal) and 4 billion 4096-byte sectors = 16TiB.

Fortunately, this limit doesn't matter much, because the only way to reach it in a 6-bay NAS with currently-available reasonably-priced drives is to have a 6x4TB array with only single-disk redundancy (RAID5), for a 20TB usable total. Single-disk redundancy in an array of that size is probably foolish; most people will choose two-disk redundancy (RAID6) for a 16TB usable array, and buy an additional NAS if they really need to expand beyond 16TB.

zamboni wrote:
The array cannot expand beyond 8TB more than the original size.

This is a limit that many people do actually reach, so I think it's the more important one. I agree that it would be better if the limit didn't exist... But you should have a backup of your data anyway, so requiring a backup in this situation doesn't seem like too much of a burden.