I recently migrated several virtual machines (VMs) from a Dell R760 ESXi host to a newer R770 with a 6760P CPU. Since the migration, I've noticed that the load and memory usage for these VMs, which include a mix of both Windows and Linux operating systems, have nearly doubled. I'm trying to understand what could be causing this increase in resource usage.
5 Answers
Make sure you're running the same version of ESXi on both hosts. Also, check if you've upgraded VMware tools after the migration, as configuration issues could also cause this kind of problem.
It might help to compare the specifications of both hosts. Additionally, check if the power settings are optimized on the R770. Sometimes, power saving modes can affect performance.
It’s also worth looking into potential I/O wait times and storage contention. Additionally, check if there's a lack of effective memory deduplication happening, as that can impact performance as well.
One possible reason for the increased RAM usage and load in your Windows VMs could be related to the CPU flags being set by your hypervisor. Sometimes, Windows VMs try to address vulnerabilities like Spectre, even when they don't need to for your current hardware setup. This can lead to higher resource consumption than necessary.
Could you share which hypervisor and its version you are using, along with details about how the migration was performed? Those details might provide clues to why you're seeing this change.
This sounds like a good place to start.