We have seen this on VMFS5 as well.
Also see:
- http://blogs.vmware.com/vsphere/2012/08/vmfs-heap-considerations.html ("As a rule of thumb, we are conservatively estimating that a single ESXi host should have enough default heap space to address around 10TB of open files/VMDKs on a VMFS-5 volume.")
- http://communities.vmware.com/thread/396522
- http://longwhiteclouds.com/2012/09/17/the-case-for-larger-than-2tb-virtual-disks-and-the-gotcha-with-vmfs/ ("Currently VMFS5 is limited to a maximum of 25TB of virtual disks open per host (Yes per host).").
I think that the VMFS3 in the value name is because it was introduced in VMFS3 (and did not exist e.g. in VMFS2).