VM Memory Reservation - When is it a good idea to set it?

[bahamut_x2]

What is a rule of thumb of deciding weather to configure memory reservation or not. I've seen alot of environments where there is no reservation but seen other environment where virtually 90% of the VMs have reservation. Most of these VMs are not mission critical.

[scott28tt]

When you want to guarantee no memory reclamation for a VM in the situation when the host is under memory pressure. But it can have implications of VM failovers in a HA cluster.

[depping · Accepted solution]

you set a reservation when you need a guarantee that a given workloads always receives the resources it demands. Basically, when demand and entitlement need to be equal. I would not set reservations on all VMs, i typically would only do it when there's a use case for it. And when you have sufficient memory, it usually even doesn't make sense, as VMs would receive the resource they demand anyway.

[berndweyand]

a special case is when you use nvidia gpu in your vm - reserving all guest memory is then mandantory

[bahamut_x2]

Thanks everyone for helping me out!

[bahamut_x2]

I was thinking same. Almost all have memory reservation and I could not see why. A 4GB RAM VM does not need reservation especially when it's a low priority server.