So lets say I have an fs with 2 1tb drives and 1 3tb drive.
Lets say one day the 3tb drive fails.
Lets say the drobo is 90% filled with data
Lets say the 3tb drive then fails.
How is the data still protected with a majority of the space coming from 1 hd?
More specificly to my setup is:
At the moment is really 4 1tb drives but I am thinking about getting a 3tb drive to fill the last hd slot. I have the 2 hd failure protection set and I started to think about what if a new 3tb drive failed and another 1tb drive… how would the other 3 1tb drives offer protection.
Do this: Drag 4x 1TB drives in the FS. The “available for data” space is 2.72 TB. Now drag a 5th 1TB drive in there, and the “available for data” space jumps to 3.63TB. Now, drag a 2TB in the place of that last one. Notice how the “available for data” space has not changed? Instead, there is now 0.9TB of “reserved for expansion” space, that you cannot use.
If you check the “dual redundancy” box, the values are respectively 1.81TB and 2.72TB, but you still end up with 0.9TB of unaccessible space.
I am pretty sure that what will happen to you is exactly the same, i.e., if you have already 4x 1TB disks, and add a 3TB, most of that extra space is going to be hidden away, waiting for you to add at least another 3TB disk (or two, if you have dual redundancy on) to unlock it.
Btw DRI people, could we please get an updated version of the drobolator with 3TB drives? That would be really helpful to start planning upgrades.
It all depends on your situation. If you are on a budget, and plan to slow upgrade all the HDDs from say, 1TB to 3TB, you can buy them one at a time spread over a couple months and pop them in when you can afford them.