----- Original Message ----- Thank you 1. Created a cluster with 1 real host, 1 fake-VDSM based host and 1 storage domain (so the storage pool will be up). 2. Created a pool with 6000 VMs that is based on template with one network interface and no disks. 3. Ran all the VMs on fake-VDSM (they were pinned to that host) At that point I had a fake-VDSM host that runs 6K VMs. Then, 1. I put all the things in my master-based setup to maintenance and removed all VMs. 2. Configured 1 cluster with this host - all the 6K VMs were added as external VMs. And on 3.6 I did the same - created a cluster only with that host (and the VMs were added as external VMs). By this, I had the exact same setup on both 3.6 and 4.0 and I didn't have anything else that could influence the measurements. Note that that's why many of the numbers presented in the post should not be considered as absolute values but only as a relative values between 3.6 and 4.0 setups. My point is that when I say that saving the statistics took 2% of the interactions with the database, this '2%' would probably be different in other environments and lower when the system does other things my system did not do. Dell optiplex 780, 16GB of RAM, 4 CPUs with 4 cores-per-CPI Both the engine and fake VDSM were running on that host. I didn't change it manually - initial and maximum heap size of 3971M No, I kept the default settings. Note that only part of these changes are in 4.0. What bothers me and worth checking on 4.0 is the memory consumption - in 4.0 we already cache VM statistics but many of the changes that probably lead of the overall decrement of the memory consumption are missing there. So it would be interesting to see what is the implication of storing more data in memory in 4.0 - if it is problematic we can easily remove this cache as it is rarely used in 4.0.