hello friends. I have a server with 10 gigabyte of ram and i can launch 10 instance with 1 gigabyte of memory. but if i know that the mean usage of ram is 100 megabyte but it can peak to 1 gigabyte i can launch 100 instance on this server because the peak usage of ram is different and 100 * 100meg=10giga byte so theoretically i can launch 100 instance but in operation the nova said no valid host was found if we said we have cloud it should be manage the usage of ram. but how openstack do it?