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ManivelR
Hot Shot
Hot Shot
‎05-17-2023 12:33 PM

ESXi 8.0 host memory usage is very high than VM usage

Hi Team,

I have a 3-node VSAN cluster and the total memory of all 3 ESXi hosts are around 2300 GB of memory.

we have allocated some 2 TB of memory to all 21 VMs running on the cluster.

Also the active memory of all the 21 VMs is using just 10 %.No VMs are not actively being used.

why my cluster usage is more than 90% ?  how to conclude this?

There is no reservation,no limit etc..

Cluster stats,

ManivelR_5-1684351865087.png

 

ManivelR_0-1684351332309.png

 

ManivelR_2-1684351558243.pngManivelR_3-1684351578919.png

ManivelR_4-1684351639274.png

Thanks,

Raj

 

 

 

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3 Replies
Tibmeister
Expert
Expert
‎05-30-2023 06:50 AM

vSAN itself will use host memory to function, and not a small amount of it either.  Here's a good KB on the subject, https://kb.vmware.com/s/article/2113954.

For instance, in my 3-node cluster, almost 40% of my RAM of each host is consumed by vSAN.  This has been contributed to high IO on a 10GBe network, so vSAN needs more RAM for caching, above the caching tier we have as well.  Just the nature of the beast.

Also, make sure you don't have HotAdd or memory locking going on.  Also check other host services to make sure there's nothing silly going on there.  I would also run the vSAN Performance Monitor to make sure you don't have any bottlenecks in the IO chain anywhere.

AnaghB
Enthusiast
Enthusiast
‎05-30-2023 07:00 AM

Hello @ManivelR ,

Please check in the Edit settings of the VM that the Memory Reservation option is checked or not. If we have used memory reservation then no matter what memory is actually used on the Guest OS the Esxi will report 100% usage of the allocated memory.

Also vSAN functionality itself consumes 30-40% of the total host memory for its own operations.

 

Anagh B
VCIX-DCV6.5, VSAN Specialist
Please mark help full or correct if my answer is use full for you
ManivelR
Hot Shot
Hot Shot
‎07-28-2023 11:17 AM

 

Thanks so much Tibmeister and Anagh B for your valuable responses.

Im sorry for the late response.I thought,no one responded back and lately(this week only) I saw both your responses.

Hi Tibmeister/Anagh B,

 

This is the VMware Engineer response.

On checking the same,customer has disabled the ballooning on the guest operating system.

Conclusion from VMware Engineer.

Enable VM Ballooning to allow the OS to better offload unused memory to the hypervisor for load balancing resources.

Thank you,

Manivel RR