Hi,
how can a VM breach the 8GB limit if it has only 8GB configured??
The configured amount of RAM is what is presented to the guest OS. If the guest OS (e.g. Windows) wants to consume more than that it will use its own memory management to accomplish this (e.g. using a swapfile inside the guest OS).
According to the "Shared memory" this is the amount of RAM that this VM shares with (at least one) other VM(s) running on the same host. ESX has a process called transparent page sharing (TPS) that continously scans for memory pages that have the same content (e.g. all zeros) in multiple VMs, and will then collaps these pages to one copy that is just referenced by all VMs using it. As soon as a VM writes to such a page it will get its own copy again.
If you want to thoroughly understand memory management in ESX I suggest that you read this paper:
http://www.vmware.com/resources/techresources/10129
Andreas
- VMware Front Experience Blog
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