Technical Tip: FortiAnalyzer BigData blade reports reduced memory size

Description

This article describes an issue where a FortiAnalyzer BigData blade reports a lower usable memory capacity than expected on the Cluster Manager page: for example, 65536 MB (64 GB) instead of the installed 131072 MB (128 GB), across 8 populated DIMM slots.

Scope

FortiAnalyzer BigData 4500F.

Solution

1. From the CMM Blade Status page, confirm the discrepancy between installed and reported memory: Navigate to Blade System -> Blade Status, select the affected blade, and check Motherboard Information -> Memory -> Memory Size against the expected total for the number of DIMMs shown under Num of DIMM.
   
   

Or from the FortiAnalyzer Blade page, SSH to each of the blades and enter the command below:

[fazbd@blade-198-x-x-x ~]$ free -h
              total        used        free      shared  buff/cache   available
Mem:          62Gi        51Gi        2.9Gi       0.0Ki        8.3i       7.4Gi
Swap:         31Gi       5.8Gi         26Gi

2. Review the blade's System Event Log for memory-related assertions: Navigate to Blade Status -> [Blade] -> Health Event Log, or export the logs, and look for entries of the form:

Memory Error   BIOS OEM   DIMM mapped out. (P1-DIMMA1) - Assertion
Memory Error   BIOS OEM   (runtime) Failing DIMM: DIMM location. (P1-DIMMA1) - Assertion
Memory Error   BIOS OEM   (runtime) Failing DIMM: DIMM location. (P1-DIMMA1) - Assertion
Memory Error   BIOS OEM   DIMM mapped out. (P1-DIMMB1) - Assertion
Memory Error   BIOS OEM   DIMM mapped out. (P1-DIMMD1) - Assertion
...
Memory Error   BIOS OEM   DIMM mapped out. (P1-DIMME1) - Assertion   [repeats 10+ times per boot cycle]

Note which DIMM slots and which processor (P1/P2) are affected, and whether the errors repeat across multiple boot cycles (indicating a persistent fault rather than a transient event).

3. This information indicates that the blade has 8 populated DIMM slots totaling 131072 MB (128 GB), giving 16384 MB (16 GB) per DIMM. Mapping out 4 of the 8 DIMMs removes 4 × 16384 MB = 65536 MB (64 GB), which accounts exactly for the reported drop from 131072 MB to 65536 MB - confirming the memory size discrepancy is fully explained by the mapped-out DIMMs, with no other capacity loss unaccounted for.

4. Cross-check against the Sensor Reading data (Sensor Reading tab) to confirm which DIMM slots report Not Present versus Normal. DIMMs mapped out by BIOS will show as Not Present with no temperature reading, distinguishing them from slots that were never populated.
   
   

5. If all affected DIMM slots are behind the same processor while the other processor's DIMMs are unaffected, treat this as a probable CPU memory-controller or socket-level fault rather than isolated DIMM failures, and prioritize hardware diagnostics accordingly.
   
   

6. Open an RMA case with Fortinet with all the information gathered to proceed with blade replacement. See Technical Tip: RMA General Procedure for FortiManager or FortiAnalyzer.