Re: vsphere upgrade 5.5U3B to 6.5 U1g- Approach for updating vmware tools and hardware

Thanks for your prompt response Andre!, and apologize for my delayed response.

With your vast field experice, would you be so kind to answer on the following?

All our hardwares are HP Proliant DL380 Gen8 or HP Proliant DL380 Gen9. connected with SAN storage (Hitachi VSP G200 / HUS110) via Fibre channel. Plan is to migrate these hosts to newly built vCenter 6.5 U1G Windows vCenter server and then upgrade the hosts to 6.5 using HPE customized image.

1. Is there a need to reconfigure or present the again the storgae to hosts when I migrate the hosts from old vCenter server (5.5) to new vCenter server 6.5?
2. Is there a need to reconfigure or present the again the storgae to hosts when I upgrade the hosts to ESXi 6.5?
3. HP Proliant DL380 Gen8 or HP Proliant DL380 Gen9 are compatible with vSphere version 6.5. Since I am using HPE custom image for upgrading the ESXi, drivers update for HBA, Multipathing are taken care by HPE image?
4. I see some users posting issues like SAN datore disappeared post upgrade ESXi host to 6.5? are there any possible issues?
5. Is it supported to run few ESXi hosts in a cluster with license assigned (5.5 license) and few unlicensed (for temporary period) during upgrade phase.
6. I have followed vmware instructions to install/configure new 6.5 Windows vCenter server (https://docs.vmware.com/en/VMware-vSphere/6.5/vsphere-esxi-vcenter-server-65-installation-setup-guide.pdf ). Are there any other parameters that I need to consider as a best practice w.r.t performance?

Thanks in advance