Upgrade to ESX 3.5 and VMFS 3.31 question

When I install a new hosts with esx 3.5, I will get the VMFS version 3.31.

But when I upgrade a 3.0.2 esx host my storage won't be upgraded to VMFS 3.31 - it is still VMFS 3.21.

It seems that VMotion Storage won't work with VMFS 3.21 only with VMFS 3.31.

Is that correct? Has anyone experieces about this topic?

So is it possible to convert storage with VMFS 3.21 to a VMFS 3.31 without deleting and reformating it?

I don't find anything in vmkfstools to convert a volume.

Thanks for any reply.