That is the correct procedure. It does not matter which drive you replace first. Be aware that the sync after the second drive will be in two stages, one to re-sync the original partitions and another to expand. Only when the second step completes will you see more space.
And if you have not yet selected drives, I suggest you do your homework. The Netgear compatibility list is so old it's useless. But many drives today, including the WD Red (but not Red Plus or Red Pro) are SMR, which can be very problematic in a RAID system, especially with BTRFS. You want CMR. The Seagate Ironwolf drives are also CMR, as are enterprise class drives not labeled "archive".
I'm aware of WD RED being SMR now. WD should never having used the name WD RED for the SMR-disks. Created (and creates) a lot of confusion and source of problems for people not knowing the change.
But the two 4TB disks I have are WD RED Plus, so CMR.
So I was correct with the procedure, I assume all can been done hot-swap ?
The actual configuration being a 2TB RAID1, there are actually two Healthy copies which makes me think I can proceed without backup ? If something goes wrong with the first HDD, I still have the second one.
The actual configuration being a 2TB RAID1, there are actually two Healthy copies which makes me think I can proceed without backup ? If something goes wrong with the first HDD, I still have the second one.
Keeping the 2 TB drives intact until the procedure completes does give you reasonable fallbacks if something goes wrong.
