I must admit, I didn’t try it (yet) but what I read in a few minutes makes this a very nice feature for NethServer as a fileserver: VDO was originally developed by Permabit Technology Corp. as a proprietary set of kernel modules and userspace tools. This software and technology has been acquired by Red Hat, has been relicensed under the GPL (v2 or later), and this repository begins the process of preparing for integration with the upstream kernel.
VDO installs within the Linux device mapper framework, where it takes ownership of existing physical block devices and remaps these to new, higher-level block devices with data-efficiency capabilities. In other words: it adds deduplication to a basic RH/CentOS server.
It might be a (very) nice feature to add once NS 7.5 is available…
More info on RH site: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/vdo