Don't run ESXi without ECC.

Yes. Non-ECC memory on a host with 20 VMs is asking for trouble. ECC isn’t optional—it’s a standard feature for servers running any virtualization workload. Without it, a single bit flip in RAM can silently corrupt data or crash the entire host.

Here’s the deal: VMware ESXi is an enterprise hypervisor. It assumes the hardware under it is reliable. Non-ECC memory will occasionally throw errors—especially under load with 20 VMs fighting for memory. Those errors can cause random host panics, VM corruption, or—worst case—data loss that you won’t catch until it’s too late. ECC catches and corrects those errors on the fly.

Motherboards and CPUs that support ECC cost a little more, but nothing compared to the downtime of a crashed host. If you’re building an ESXi host for production, don’t even consider non-ECC. It’s not a corner to cut.