Data management often includes RAID because  users want to be sure that their data they are working with won’t be corrupted,  damaged or lost. Redundancy is the key notion when it comes to data production.  On the other hand, some users opt and set up their NAS for better performance  gains. Nested RAID (hybrid RAID) is the solution for those who seek both   performance and redundancy. Although this configuration is less common, it  presents a big advantage compared to single RAID configuration. In short,  Nested RAID presents a balance between performance and redundancy level array. 

Nested RAID: Intro 

Common   Nested RAID configuration are RAID-01 and RAID-10, we’ll use these  configurations to go into more details about benefits and requirements of  Nested RAID. To elaborate, the number on the left is the lowest RAID and the  right number is the top RAID. In most cases, RAID 0 is preferred on top and redundancy  is on bottom given that fewer disks are needed to rebuild if disk failure  occurs. 

RAID-10 and RAID-01: characteristics 

RAID-01

RAID-10

To review 

Nested   RAID configurations allow the ability to add enhancements compared to standard  RAID levels. This configuration opens doors for NAS users who seek something  different than the standard RAID levels but users should be aware that there  are some downsides as well. 

A   concept that comes to mind is, “give a little here, take a little there” since  getting more performance or redundancy sacrifices storage space, minimum  requirement of disks, or if a disk fails data is lost for RAID-01 to name a  few. 

To  add, Nested RAID is not only restricted to two digits, they can use “RAID-XYZ”  if appliance allows. Overall, Nested RAID offers more flexibility to NAS users  as some opt for a balance between performance and redundancy instead of a  single RAID array.