I have been running 2 Synology’s for quite some time now. The first one has 4 bays, and I loaded it up with 4 x 8TB drives. In a raid 5 configuration, that gave my just under 22Tb usable. I was running out of space fast and I was able to pickup another Synology 4 bay, but this one already has 3 x 2TB drives. This helped for a little while, but i was again running out of space.
Luckily with all of the Sales leading up to Black Friday, i was able to pickup 3 x 12TB drives and replaced them 1 by 1.
After Replacing the 1st drive, it took about 4-5 hours to rebuild the array. I then replaced the 2nd drive and it took another 4-5 hours to rebuild the array, but this time when it was done, it expanded the capacity to a little over 12Tb which took another hour. (Very Interesting… )
I finally was able to replace the 3rd drive and it took another 4-5 hours to rebuild, but this time at the end it restarted the rebuild. That time it took 3 days and when it was done, it Expanded the capacity again for another couple hours.
When it was all said an done, I had this one sitting at just under 22TB usable, but i still have a spare bay when the drives go on sale again.
That will keep me going for awhile.