Corrupt Boot - "Err: Could not mount root RAID d"

For most users, the best RAID format is to use the default XRAID.  That can be expanded w/o data loss, and it has protection for a single disk failure.

If you want maximize storage space and don't care about expansion or protection from a disk failure, then the best option for that is to use flexraid and create one volume for each disk.  

To do that, you need to start over and set up the NAS again.  Remove all disks but the first, then do a factory reset using the boot menu.  You have a 10 minute window to configure the system for flexraid using RAIDar.

Details are in the hardware and software manuals for your ReadyNAS here: http://downloadcenter.netgear.com/en/product/RNDP4000%20(ReadyNAS%20Pro%204)#searchResults

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JimmyChen wrote:

?. Just put in & read the data inside (with NTFS format).

 

Your NAS doesn't use NTFS.  It uses EXT.  When you insert a disk into the NAS, the data on it will be wiped.  

The NAS doesn't let you create a "library" of hard drives that you can insert/remove on demand.  The disks need to remain in place after you create the volumes.