vSphere 5.0 can be confgured to enable VMware ESXi host swapping to a solid-state disk (SSD). In the low host memory–available states (high memory usage), where guest ballooning, transparent page sharing (TPS) and memory compression have not been sufcient to reclaim the needed host memory, hypervisor swapping is used as the last resort to reclaim memory from the virtual machines. vSphere employs three methods to address limitations of hypervisor swapping to improve hypervisor swapping performance.
1. Randomly selecting the virtual machine physical pages to be swapped out. This helps mitigate the impact of VMware ESXi pathologically interacting with the guest operating system’s memory management heuristics. This has been enabled from early releases of VMware ESX.
2. Memory compression of the virtual machine pages that are targeted by VMware ESXi to be swapped out. This feature, introduced in vSphere 4.1, reduces the number of memory pages that must be swapped out to the disk, while reclaiming host memory efectively at the same time and thereby benefting application performance.
3. vSphere 5.0 now enables users to choose to confgure a swap cache on the SSD. VMware ESXi 5.0 will then use this swap cache to store the swapped-out pages instead of sending them to the regular and slower hypervisor swap fle on the disk. Upon the next access to a page in the swap cache, the page will be retrieved quickly from the cache and then removed from the swap cache to free up space. Because SSD read latencies are an order of magnitude faster than typical disk access latencies, this signifcantly reduces the swap-in latencies and greatly improves the application performance in high memory over commitment scenarios.
In this video I’ll show you how SDD storage is detected by the ESXi host after adding a new datastore. You will also learn how to configure VMware ESXi host swapping and redirecting virtual machine swap files to solid state storage.
