This is a quick blog to discuss where vSphere is at with memory management today. vSphere has many mechanisms to reclaim memory before resorting to paging to disk. Let’s briefly look at these methods.
Memory Reclamation
- Transparent Page Sharing (TPS)
- Think of this as deduplication for memory. Identical pages of memory are shared with many VM’s instead of provisioning a copy of that same page to all VM’s. This can have a tremendous impact on the amount of RAM used on a given host if there are many identical pages.
- Balooning
- This method increases the memory pressure inside the guest so that memory that is not being used can be reclaimed. If the hypervisor were to just start taking memory pages from guests, the guest Operating Systems would not react positively to that. So, balooning is a way to place artificial pressure on the guest VM so that the VM pages unused memory to disk. Then, the hypervisor can …
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