before upgrading to 6, Does the Storage needs to be upgraded or at least support vvol before upgrading esxi to 6?
you can check here if your storage is supported:
VMware Compatibility Guide: System Search
with vpshere 6 they work still with vmfs5 so normally you don't need to "upgrade" your storage
Please go through following documentation for Upgrade Requirements and ensure your system is prepared for vCenter Server 6.0 upgrade
Regards