XCPU’s Guide To RAID

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What are nested RAIDs?
To gain performance and/or additional redundancy the standard RAID levels can be combined to create hybrid or Nested RAID levels.
RAID levels 01, 10, 50, and 53 are all examples of nested RAIDs. They are more commonly known by 0+1, 1+0, 5+0 and 5+3 respectively.

Learn more about that here.

Lets take a look at two examples of nested RAIDs.

RAID 0+1

RAID Level 0+1 requires a minimum of 4 drives to implement

A RAID 0+1 (also called RAID 01, not to be confused with RAID 1), is a RAID used for both replicating and sharing data among disks. The difference between RAID 0+1 and RAID 1+0 is the location of each RAID system — RAID 0+1 is a mirror of stripes. The size of a RAID 0+1 array can be calculated as follows where n is the number of drives (must be even) and c is the capacity of the smallest drive in the array:

Consider an example of RAID 0+1: six 120 GB drives need to be set up on a RAID 0+1. Below is an example where two 360 GB level 0 arrays are mirrored, creating 360 GB of total storage space:

  RAID 1
           RAID 0                     RAID 0
    .—————–.        .—————–.
 120 GB   120 GB   120 GB   120 GB   120 GB   120 GB
   A1       A2       A3       A1       A2       A3
   A4       A5       A6       A4       A5       A6
   A7       A8       A9       A7       A8       A9
   A10      A11      A12      A10      A11      A12

 Note: A1, A2, et cetera each represent one data block; each column represents one disk.

RAID 1+0

Sometimes called RAID 1+0, or RAID 1&0, is similar to a RAID 0+1 with exception that the RAID levels used are reversed — RAID 10 is a stripe of mirrors. Below is an example where three collections of 120 GB level 1 arrays are striped together to make 360 GB of total storage space:

      RAID 0
      RAID 1            RAID 1            RAID 1
    .——–.        .——–.        .——–.
 120 GB   120 GB   120 GB   120 GB   120 GB   120 GB
   A1       A1       A2       A2       A3       A3
   A4       A4       A5       A5       A6       A6
   A7       A7       A8       A8       A9       A9
   A10      A10      A11      A11      A12      A12


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