When working with MegaRAID controllers, the command /opt/MegaCli -CfgDsply -a0 often produces confusing output regarding RAID levels. The typical output format:

RAID Level : Primary-1, Secondary-3, RAID Level Qualifier-0

This doesn't directly correspond to standard RAID terminology, leading many administrators to question whether they're actually running RAID 3 (which would be highly unusual in modern setups).

The correct interpretation is:

• Primary-1: Indicates RAID 1 (mirroring) at the span level
• Secondary-3: Means there are 3 spans in the array
• Qualifier-0: Shows these spans are striped (RAID 0) together

This configuration actually describes a RAID 10 (1+0) setup with three mirrored pairs striped together. Here's how to verify this programmatically:

# Get detailed RAID configuration
/opt/MegaCli -LDInfo -Lall -aALL | grep -E "RAID Level|Number Of Drives|Span"

# Expected output for RAID 10:
RAID Level : Primary-1, Secondary-3, RAID Level Qualifier-0
Number Of Drives : 6
Span Depth : 2

For absolute certainty, combine MegaCli output with alternative tools:

# Using megasasctl for cross-verification
megasasctl | grep -A 5 "Virtual Drive"

# Sample expected output:
Virtual Drive 0:
  RAID Level: raid10
  Size: 5.46TB
  Number of Drives: 6

Here's a Python script to parse and translate MegaCli output:

import re

def interpret_raid_level(raw_output):
    match = re.search(r"Primary-(\d), Secondary-(\d),.*Qualifier-(\d)", raw_output)
    if not match:
        return "Unknown RAID configuration"
    
    primary, secondary, qualifier = map(int, match.groups())
    
    if primary == 1 and qualifier == 0:
        return f"RAID 10 ({secondary} spans)"
    elif primary == 0 and secondary == 0:
        return "RAID 0"
    elif primary == 1 and secondary == 0:
        return "RAID 1"
    elif primary == 5 and qualifier == 0:
        return "RAID 5"
    else:
        return f"Complex RAID (Primary-{primary}, Secondary-{secondary}, Qualifier-{qualifier})"

# Example usage:
mega_output = "RAID Level : Primary-1, Secondary-3, RAID Level Qualifier-0"
print(interpret_raid_level(mega_output))  # Output: RAID 10 (3 spans)

• MegaCli uses non-standard terminology that combines span and RAID level information
• Primary-1 + Qualifier-0 always indicates RAID 10 configuration
• The Secondary number represents the number of spans (mirrored pairs) in RAID 10
• Always cross-verify with physical disk count and alternative tools

For comprehensive monitoring, consider implementing regular checks that compare MegaCli output with your actual storage requirements to catch any configuration drift.

---

When running /opt/MegaCli -CfgDsply -a0, you might encounter this cryptic output:

RAID Level : Primary-1, Secondary-3, RAID Level Qualifier-0

At first glance, this appears contradictory - RAID 3 is rarely used in modern storage systems. Let's dissect what this actually means.

The syntax represents nested RAID levels in LSI's implementation:

• Primary: The RAID level applied within each span (RAID 1 in this case)
• Secondary: The number of spans (3 in this example)
• Qualifier: The RAID level applied across spans (RAID 0 here)

This configuration translates to:

[ (RAID1) + (RAID1) + (RAID1) ] → RAID0

Which is effectively RAID 10 (1+0) when using two disks per RAID1 set, or a more complex nested RAID when using more disks.

Use this MegaCli command to validate physical disk arrangement:

/opt/MegaCli -PDList -aALL | egrep "Raw Size|Device ID"

And check virtual drive details:

/opt/MegaCli -LDInfo -LALL -aALL | grep -i "strip\|number"

For clearer output, consider using megasasctl (for newer SAS controllers):

megasasctl -d

Example output comparison:

MegaCli:   RAID Level : Primary-1, Secondary-3, RAID Level Qualifier-0
megasasctl: RAID10 (1+0) with 3 spans

Here's a bash script to interpret MegaCli output:

#!/bin/bash
RAID_INFO=$(/opt/MegaCli -CfgDsply -a0 | grep "RAID Level")

IFS=', ' read -r -a raid_parts <<< "$RAID_INFO"
primary=${raid_parts[2]#*-}
secondary=${raid_parts[4]#*-}
qualifier=${raid_parts[7]#*-}

case "$primary-$qualifier" in
   "1-0") echo "RAID 10 (1+0) with $secondary spans" ;;
   "0-1") echo "RAID 01 (0+1)" ;;
   "5-0") echo "RAID 50 with $secondary spans" ;;
   *) echo "Complex nested RAID configuration" ;;
esac

For modern systems, consider these alternatives:

• storcli (successor to MegaCli)
• ssacli (for HPE servers)
• lsblk and mdadm (for software RAID)