The upgrade path to follow depends on which version of vRealize Log Insight is installed and the version you are upgrading to.
You can upgrade vRealize Log Insight to version 8.1 from 4.8 or 8.0. Upgrades to vRealize Log Insight 8.0 or earlier must be done incrementally. For example, to upgrade from version 4.5 to 4.7, you apply the 4.6 upgrade to 4.5 and then upgrade from 4.6 to 4.7. You must upgrade to each intermediate release.
You can also view supported upgrade paths on the VMWare Product Interoperability Matrixes site.