As I thought I said before, the straightforward path is to turn X-RAID back on, and then hot-insert your new disk into an empty slot.
The NAS should detect it, and automatically add it to the array. You'll end up with 3x3TB RAID-5 volume that has 6 TB of space (twice what you have now).
Note that X-RAID is currently off on your system (you need to click on the X-RAID control to re-enable it). When it's enabled there is a green stripe across the X-RAID control.
So for example, I drop in 3, 3TB HDD's. You look on the right side, it shows:
XRaid
Capacity: 5.44 TiB
Protection: 2.73 TiB
Unused: 0 B
Level: X-RAID (raid5)
A HDD rated capacity for a few reasons is not quite what is shown on the Box or sticker of the drive. A single 3TB HDD works out to about 2.72TB. So in RAID 5, you have 2 drives added together for storage and the 3rd is redundancy. With RAID Magic, if ANY of those 3 HDD fails, you can in fact still use your NAS. I've been using mine as it's been rebuilding as I add larger 8TB drives into mine. 1 Rebuild, takes about 24 hours, then a second one, which is almost finished. So 1 drive fails, you can pull it, install a new HDD of equal or greater size and the NAS will rebuild that drive from the Data on the other HDD's.
This is the main reason to have a NAS over a basic external HDD.
Now you could leave it using FLEX-RAID 5 if you want which is basically like X-Raid 5. The storage results would be the same.
But you can go through all the different ones and see the results.
Flex-Raid0
Capacity: 8.17 TiB
Protection: 0 B
Unused: 0 B
Level: Traditional RAID 0
But say you have 2, 3TB HDD and you add 2, 8TB HDD's to your NAS. This is where XRaid benefits over Flex Raid really comes into play.
XRaid
Capacity: 12.7 TiB
Protection: 7.28 TiB
Unused: 0 B
Level: X-RAID (raid5)
This is Flex Raid.
Capacity: 8.16 TiB
Protection: 2.73 TiB
Unused: 9.09 TiB
Level: Traditional RAID 5
As you can see, you lose 9.09TB in space with FLEX-Raid!!!! So it's normally best to use XRaid. I would switch to XRaid, let it do it's thing, when done, just pop in the new HDD. Do you have your Data backed up? Did you use FlexRaid 0? I would back up, switch to XRaid, then pop in the new drive. It should know what to do with it.
My old NAS, I started with 2 in XRaid, which was Raid1. Clone of the first HDD. After a couple months, I popped in a 3rd HDD, it changed over to XRaid 5. I gained more space at this point. Any of the 3 HDD could fail, I could pull it and replace it with a new one of equal or greater size. It was a year later that I added a 4th HDD. Just popped it in and the NAS grew in more storage. Now any 1 of the 4 HDD could fail and I could new a new HDD swap.
At that point, it was an old, already pretty slow ARM ReadyNAS. I upgraded to a much more expensive Commercial NAS with an Intel CPU in it and 6 bays. But the new NAS used a different disc format should I had to back up that old NAS to other HDD's I had. Swap those 4, 3TB WD RED drives to my new NAS and now I had 2 free spots to grow. My first WD RED drive I installed was back in Jan 17th 2013. 5 years ago and the HDD's still work great and show zero erros. I later installed a couple Seagate 3TB, NAS drives. One of those shows like 3 ATA errors, but it's been like that for the last couple of years. Those 6, 3TB drives gave me just over 13TB of space.
This last Sunday I notice Best Buy had a sale of the 8TB WD Easyshare external drives at $129 each. It's since gone back up to $199. Early on these were RED Label drives. Now they're White Label drives. Which from what I hear are RED drives. You want the ones with 256 Gig Cache, not 128. Mine are 256. I ripped them from those external cases to pop into my NAS. They seem to be working great. Much cheaper than WD RED 8TB drives from Amazon at $250 a pop. But it may not work on some NAS units or some computers. Without some slight mod to 1 power pin. It worked just fine in my ReadyNAS. Have to keep my eyes open for another price drop. I should have gotten at least 1 more. My 2, 3TB Red drives are still good and can be used to replace a bad 3TB drive in the future.
It is funny how these company's slap a HDD into a case with a USB controller, etc and it's CHEAPER than just buying a bare HDD. I've seen Seagate do the exact same thing. You can to know what you're getting. I think WD other My Book which is also external drive and 8TB is using their Blue drive I believe. You don't want that one for your NAS!!! It's $30 cheaper than the current Easystore price. Don't get it!!! This is internet research in action.
