The minimum supported network throughput in Gb/s for each host in an all flash vSAN cluster based on the vSAN Original Storage Architecture (OSA) is 10.
Reference:
vSAN Express Storage Architecture (ESA) are only supported with 25Gbps and higher connection speeds. ESA ReadyNodes configured for vSAN ESA will be configured with 25/50/100Gbps NICs. vSAN OSA all-flash configurations are only supported with a 10Gb or higher connections. One reason for this is that the improved performance with an all-flash configuration may consume more network bandwidth between the hosts to gain higher throughput. https://core.vmware.com/resource/vmware-vsan-design-guide#sec6815-sub3