We all know that the data never shrinks, only expands. As of AOS 5.0, hot expand of VM disks is supported. All you have to do is expand the volume group via Prism UI or CLI (either aCLI or nCLI - chose your preferred method) and then extend the disk in the disk manager within guest OS itself.

aCLI:

nutanix@cvm$ acli vg.disk_update <Volume Group name> <disk index> new_size=<size of disk>

nCLI:

nutanix@cvm$ ncli volume-group update-disk uuid=<Volume Group UUID> index=<disk index> size-mib=<Size of disk in MiB>

For detailed explanation and caveats please refer to:
KB-3638 Expand volume group disk size on Windows OS
KB-5832 AHV | How to expand a Windows VM disk