Hello I'm using ProxMox as virtualization, from verson 2.x. For around 20 servers (most of them are Centos machines) for different services (Zimbra, Apache, MariaDB, PostgreSQL, EDB, ..) and also for MS servers (AD, Exchange, fileserver, MSSql Express, .). They all are running on 5-6 HW servers, different brands and all of them are pretty old. As backup use Synology NAS and nfs with 10gb fc to FC switch. So speed for backup really is not a problem. I slowly moving sata disks to ssd, in same hardware and this is really big advantage in speed. In time of changing disks move virtual machines to other hypervisors. HW Raid5 is really nice with ssd. In 3 years of changing to ssd disks only one fail, but system running and change of disk without downtime ... If I want to test, move, . backup and restore is not an issue. For this year plan is to put one NAS to other location for disaster . ProxMox and software defined storage on 4-5 machines I think for us is the best solution. In point of maintaining there is no problem with upgrading from one release to other - now is version 6.x. Only issue is probably my knowledge how to put this together. All the best Blaz