The amount of historical data displayed in a chart depends on the collection interval and the statistics level that are set for vCenter Server.
As part of the performance improvements in vSphere 6.0, some cluster and resource pool metrics that are displayed in performance charts are stored in a more efficient way so that they are loaded and displayed faster. Unless vCenter Server is set to collect level 4 statistics this might result in missing level 2 and level 3 cluster and resource pool statistics for past historic periods after you perform an upgrade to vSphere 6.0. These statistics are not affected for future periods.
The affected cluster and resource pool metrics include: