Details
This article provides a recommendation to upgrade your on-disk format version as early as possible before upgrading vSAN to 7.0 Update 1.vSAN is retiring the V1 on-disk format version, which will make the disks unrecognizable is still running V1.
Solution
VMware recommends to upgrade your on-disk format version prior to upgrading VSAN to 7.0 Update 1.For more information on upgrading on-disk formats, see Upgrade vSAN Disk Format Using vSphere Web Client.For more information regarding on-disk format/vSAN compatibility see Understanding vSAN on-disk format versions and compatibility (2148493)Also, see Removing unmounted V1 disk groups after upgrading to ESXi 7.0 Update 1 fails (77154) if on-disk format wasn't upgraded prior to the vSAN upgrade to 7.0 Update 1.
