FortiGate
FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
ahernandez_FTNT
Description
Usually different part numbers in the same model of unit implies internal changes, including hard disk. This does not necessary means the HA can not be established properly between units with different P/N.

Cluster can be formed properly between two units with different mark/model of hard disk as long as the size of their mounted partition is the same.

Solution
To confirm if two units of the same model and generation but with different P/N can form a cluster properly, execute the following command and compare the hard disk details:
execute disk list

Example:

Unit 1: FortiGate 200D | Generation: 02.00 | P/N: P11534-05
UNIT1# execute disk list
Disk Internal        ref:  16  59.6GB    type: SSD [ATA SanDisk SD6SA1M0] dev: /dev/sdb
partition ref:  17  58.7GB,  34.4GB free  mounted: Y  label: 01652F63096029E8 dev: /dev/sdb1 start: 63

Unit 2: FortiGate 200D | Generation: 02.00 | P/N: P11534-08-02
UNIT2# execute disk list
Disk Internal        ref:  16  59.6GB    type: SSD [ATA 64GB SATA Flash] dev: /dev/sdb
partition ref:  17  58.7GB,  58.5GB free  mounted: Y  label: 53EBB2E22BBF7686 dev: /dev/sdb1

These two units have different hard disk model.  Therefore, their P/N are different. However, they can establish an HA together properly because their partition size is the same.

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