We have Hyper-V running on 2012 R2, I noticed that whenever the VMs memory usage spikes for whatever reason, they HV will assign more RAM to them, but when the VM's are idle, the HV doesn't reclaim the RAM that was assigned, thus, causing constant resource shortages.
Total RAM is 32 GB, 4 VMs total, 3 of them have a minimum of 2 GB and 8 GB max, the 4th has a minimum of 2GB and 20GB max.
VMs 1-3 are DC, File Server and App server but they rarely go over 4GB, still, when they're idle, allocated RAM remains at 4GB
VM 4 is a backup server, each backup job takes up to 2GB so it can easily reach the 20GB limit, this server works mainly at night, with only 2 backups running during the day, so technically there shouldn't be a resource issue
But since RAM is not dropping once the backups are done, we are constantly finding paused/locked VMs in the morning.
I couldn't find a similar issue posted before so I decided to ask and see if anyone else has gone through this.