Increasing capacity 5D3

I have a 5D3 with four 4TB enterprise drives. I need to increase my storage capacity. I want to replace the four original drives with four new Seagate Enterprise Capacity 3.5 HDD 10TB drives without losing data.

I am hoping to be able to add a 5th drive, then wait for a while to let the data be distributed in the array then start swapping out the old 4TB drives one at a time.

Back in the day when I was running a simple Raid 10 array, I could just start swapping drives with no problems. My old drives were still readable and I stored them in a safe. From what I have read Drobo does not use the same kind of duplicate sets of data so the drives are only usable if they are all loaded.

What is my best option? I really like the speed of the 5D3 on my iMac Pro, but I had not anticipated the problems that I now face trying to increase capacity and archive my older files. I appreciate any pointers you may have.

No quick and easy way, other than a drive at a time. Drobo uses a RAID 5 or 6 depending on how you have it configured.

Unfortunately this is true. You have to remove 1 drive at a time, put in the new drive, wait for your RAID to rebuild and then do the next drive.

Off topic, can you comment on the speed you are getting with your 5D3? I have new WD Red drives in mine (6 + 6 + 6 + 8 + 8), plus a 500GB Samsung SSD for cache; I am seeing < 70 MB/s for read and write, using Black Magic Speed test. Are you getting better performance than that?

Thanks, in advance.