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Only upgrade (not downgrade) of most components is supported while still considering it a ReadyNode:
It could still be a supported vSAN configuration if all the swaps/addition cache/capacity devices are on the vSAN HCL but it wouldn't technically be a ReadyNode with the changes you suggest.
Thanks for your advised, the the reference link that you gave provided the all answer of my questions.
I think custom of spec which i've plan above is technically working for vSAN , but i'm not sure about the Support of vmware cause it's violating policy
Well the first thing I would say that if indeed lowering the CPU/Memory capabilities of the server made it be considered 'not a ReadyNode' then technically it wouldn't be supported to use SAS-expanders.
This is a fairly corner-case - I would advise contacting vSAN Hardware PM at firstname.lastname@example.org who may be able to provide further clarification, let us know if there are any further insights from this.