RAID level confusion (MegaCli vs megasasctl output)

Solution 1:

I think the table is wrong.

Because RAID 10 is a stripe (RAID-0) of a Mirror (RAID-1)
Primary -> RAID-1
Secondary -> RAID-0

RAID 0 -> RAID 1 -> DISK
                 -> DISK
       -> RAID 1 -> DISK
                 -> DISK

Solution 2:

Just for more background info, you can use the command:

megacli -CfgDsply -aALL

To get a little more info, including disk groups, a info about spans. Below is my commented/indented output of selected lines (from a Windows machine, but it's pretty close).

Note that for the first disk group ("SPANNED DISK GROUP: 0"), it says RAID 10 eventhough it's just two disks mirrored. Ie., it's really RAID 1, but it seems to say RAID 10.

So looking at the 2nd disk group ("SPANNED DISK GROUP: 0"), if span 0 and span 1 were each just 2 concatenated/striped disks, then the next level up could be mirroring them and still report RAID10 (same as the first disk group). Probably, it's implemented as RAID10 not RAID01, but either way it would still report the same total size for the virtual drive. There's just not enough information here to know for sure.

Adapter: 0
Product Name: PERC H710P Mini

Number of DISK GROUPS: 2

DISK GROUP: 0                          # Simple 2 disk RAID for operating system
  Number of Spans: 1

  SPAN: 0
    Number of PDs: 2
    Number of VDs: 1
    Virtual Drive Information:
    Virtual Drive: 0 (Target Id: 0)
    Name                :
    RAID Level          : Primary-1, Secondary-0, RAID Level Qualifier-0
    Size                : 837.75 GB    # Size of the virtual drive matches the size of each drive
    Mirror Data         : 837.75 GB    # indicating RAID 1 mirroring
    Number Of Drives    : 2
    Span Depth          : 1

    Physical Disk: 0
      Drive's position: DiskGroup: 0, Span: 0, Arm: 0
      Device Id: 0
      Sequence Number: 2
      Coerced Size: 837.75 GB [0x68b80000 Sectors]

    Physical Disk: 1
      Drive's position: DiskGroup: 0, Span: 0, Arm: 1
      Device Id: 1
      Sequence Number: 2
      Coerced Size: 837.75 GB [0x68b80000 Sectors]


# The "spanned disk group 0"  below could be either:
#   device_id 2 mirrored with device_id 3, making span 0
#   device_id 4 mirrored with device_id 5, making span 1
#   then span 0 and 1 striped together
# or
#   device_id 2 striped/concatentated with device_id 3, making span 0
#   device_id 4 striped/concatentated with device_id 5, making span 1
#   then span 0 and 1 mirrored together

SPANNED DISK GROUP: 0             # This is a different disk group from the one above because of
  Number of Spans: 2              # the word "spanned".

  SPAN: 0
    Number of PDs: 2         
    Number of VDs: 1
    Virtual Drive Information:
    Virtual Drive: 1 (Target Id: 1)
    Name                :VD_1        # This virtual drive info is the same for both spans, indicating
                                     # the RAID info really associated with the disk group, rather
                                     # than the span
    RAID Level          : Primary-1, Secondary-0, RAID Level Qualifier-0
    Size                : 1.635 TB  
    Mirror Data         : 1.635 TB  
    Number Of Drives per span:2
    Span Depth          : 2

    Physical Disk: 0
      Drive's position: DiskGroup: 1, Span: 0, Arm: 0
      Device Id: 2
      Sequence Number: 2
      Coerced Size: 837.75 GB [0x68b80000 Sectors]

    Physical Disk: 1
      Drive's position: DiskGroup: 1, Span: 0, Arm: 1
      Device Id: 3
      Sequence Number: 2
      Coerced Size: 837.75 GB [0x68b80000 Sectors]

  SPAN: 1
    Number of PDs: 2
    Number of VDs: 1
    Virtual Drive Information:
    Virtual Drive: 1 (Target Id: 1)
    Name                :VD_1        # This virtual drive info is the same for both spans, indicating
                                     # the RAID info really associated with the disk group, rather
                                     # than the span
    RAID Level          : Primary-1, Secondary-0, RAID Level Qualifier-0
    Size                : 1.635 TB   
    Mirror Data         : 1.635 TB   
    Number Of Drives per span:2
    Span Depth          : 2

    Physical Disk: 0
      Drive's position: DiskGroup: 1, Span: 1, Arm: 0
      Device Id: 5
      Sequence Number: 2
      Coerced Size: 837.75 GB [0x68b80000 Sectors]

    Physical Disk: 1
      Drive's position: DiskGroup: 1, Span: 1, Arm: 1
      Device Id: 4
      Sequence Number: 2
      Coerced Size: 837.75 GB [0x68b80000 Sectors]

Solution 3:

They seem to be both indicating a RAID 10 to me. Please have a look at http://www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf from page 13 for a nice description of what you got as output from megacli.