There are many memory optimization configuration options in vSphere 5.0. VMware has released a new whitepaper that describes the basic memory management concepts in ESXi, the configuration options available, and provides results to show the performance impact of these options. In VMware vSphere 5.0, a share-based memory management mechanism is used to enable both performance isolation and efficient memory utilization. The algorithm relies on a working set estimation technique which measures the idleness of a VM. Ballooning reclaims memory from a VM by implicitly causing the guest OS to invoke its own memory management technique. Transparent page sharing exploits sharing opportunities within and between VMs without any guest OS involvement. Memory compression reduces the amount of host swapped pages by storing the compressed format of the pages in a per-VM memory compression cache. Swap to SSD leverages SSD’s low read latency to alleviate the host swapping penalty. Finally, a high level dynamic memory reallocation policy coordinates all these techniques to efficiently support memory overcommitment.
The whitepaper covers things like:
- An ESXi memory management overview
- Memory reclamation
- Memory allocation management for multiple virtual machines
- Performance evaluations
- Best practices
- And more…