Two weeks ago, my NAS suddenly emitted a high-pitched, enervating sound, and the indicator of one of the hard disk trays blinked nervously. The info line in the display screamed 'hard disk failure, RAID degraded', my wife's face was frozen in terror, the cats stared at me with eyes as big as saucers, and I was close to a heart attack. What prevented the disaster was my sudden realization that I had made a backup copy just a week ago...
In any case, since I've set up a RAID 5 for the four disks in my NAS, nothing was lost yet. And I actually wanted to upgrade the disks for quite some time, since their total capacity of somewhat less than 6 TB was close to be exhausted. Hence, I ordered four 3 TB NAS disks right away, but kept brooding over the question how to create backup copies when the capacity would be close to 9 TB. Should I really invest in a second NAS? Naa: I really don't need another always-on device in my flat.
The solution was so simple. With three 2 TB disks freed from the NAS, two 1 TB disks just lying around, and 6 TB in three USB hard disks, there's already more than enough disk space to back up the NAS. And the orphan SATA disks can be utilized by simply employing a docking station! Yes, it's that easy.
I've acquired this one and, just for he fun of it, partioned and formatted three of the orphan disks. Copying data from the NAS (mounted via cifs over a GB switch) worked flawlessly.
When the new disks arrived, I exchanged one by one, as one does for a RAID. It always took a few hours to rebuild the system, so I simply waited from one night to the other. Finally, it just took 10 min to expand the RAID to the larger disk size. The almost 9 TB should suffice for some time. :)