Standby firewall has less memory utilisation than the active firewall.

[shiv_poch]

We have a clusterXL firewall (HA mode) the primary firewall has always been the active firewall, preempt mode is disabled.

Failover happened weeks ago which made the secondary firewall active.

We noticed however that even after the failover, the memory utilsation is the same for both.

Is this expected? primary firewall's average memory is at 50% and the secondary is at 40%. 

after failover, the primary firewall which is now the standby, still has the same  50% memory.

And the secondary firewall which is now the active firewall is still at 40% memory.

Is this expected? Can a standby firewall have less memory than the active firewall?

[Chris_Atkinson]

What is the uptime of both units?

Potentially the old primary has more memory assigned to cache etc.

In summary it's not necessarily indicative of an issue in my opinion.

[shiv_poch]

Uptime of both is 370 days.

Is it recommended to do maintenance reboot?

So it should not be an issue if the standy firewall has a higher memory than the active firewall as it could be due to cache/buffer memory?

and we also noticed that overtime the memory utilisation increases even when there's no significant increase in the traffic.

[PhoneBoy]

It's possible there is a relatively slow memory leak somewhere that occurs under specific conditions.
Regardless, if it's been 370 days since your last reboot, and probably longer since a JHF was applied, it might be worth taking the opportunity to apply the latest recommended JHF for your release, which will require a reboot.

[_Val_]

If you are using a system command to gather memory utilization, or check it via SmartConsole, you see memory utilization reported by OS. This data is not always reliable. You should only be concerned if use goes above 90%.

To check actual memory use, run "fw ctl pstat" command from expert mode on both members. That said, in any case, with the utilization mentioned above, you should not be concerned. It is OS that is most probably reporting inaccurate data. 

[Dario_Perez]

How many RAM they have? Also which blades are enabled?

sample if you have R80.30, 8GB RAM and full blades, maybe that appliance even without traffic have more than 40% utilization.