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vishnuas
Contributor
Contributor

vSAN failing with different RAM configurations of ESXi hosts

Hi,

I was exploring vSAN 6.7U3 with evaluation license and I came across a scenario when the 'configure' step in vCenter fails whenever I increase the RAM allotted to the ESXi host.

I have an All-flash vSAN configuration with 2 ESXi hosts each having 2 disk groups (each disk group with capacity tier 12TB and caching tier 2TB).  Each ESXi host is allotted 7.5GB RAM. The physical machine hosting the ESXi host has 64GB RAM. In this trial, the vcenter configuration completes successfully, creating the vSAN datastore.  

But for the same configuration when I increase the ESXi host's RAM from 7.5GB to 15GB, 'configure' step in vcenter fails at 'disk group creation' resulting in 'Operational Health' error as seen in the picture below. I have tried fresh installation of vCenter and ESXi hosts, but still shows the same error. When I decrease the RAM back to 7.5GB, everything works perfectly.

From the logs, I found the error "Failed to initialize the memory for the disk group" but I have not been able to understand the reason behind this error.

I kindly request any help in understanding and solving the issue. Thanks in advance

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T180985
Expert
Expert

Its unclear why it worked with the lesser amount of memory but it looks like you will need to assign more memory for vSAN to function. See the memory consumption guide below:

VMware Knowledge Base

Please mark helpful or correct if my answer resolved your issue. How to post effectively on VMTN https://communities.vmware.com/people/daphnissov/blog/2018/12/05/how-to-ask-for-help-on-tech-forums
vishnuas
Contributor
Contributor

Hi,

Thanks for the quick reply. As mentioned in the link, I tried different scenarios with RAM greater than 22GB (one disk group per ESXi host) and every case worked. Thanks again for pointing to the document.

Still curious why it is working with 7.5GB RAM. I have tried up to 3 disk groups per ESXi host and vSAN works with 7.5GB RAM.

Thanks,
Vishnu

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