VMware ESXi memory allocation to VMs

[shrrapidwebglob]

Hi,

I am not from VMware background but would like to get clarification on memory allocation on VMware ESXi host. I am seeing some weird scenario with one of our ESXi 5.5 host. It has physical memory of 16G total, but I am able to allocate upto 1TB memory to Virtual machines. How can be its possible? Can someone please clarify? Thanks!

[daphnissov]

An allocation is not a guarantee of resource availability, but like a "promise". I can bet you $1M and you can accept the bet, but if I lose there's nothing saying I actually have $1M to pay you. Same concept works with resource allocation in a virtualized world.

[shrrapidwebglob]

Oh okay.. So there is no point in allocating more than 16G then ??

[daphnissov]

Yes, and depending on what else that host is running you may not even want to allocate that much.