| i don't know what the penetration of it looks like, but on the vsphere/esxi side there are also a number of really expensive addon features that i have not seen reproduced in open source software. 1. vmotion + storage vmotion - you can live migrate a vm from one hypervisor host machine to another. you can also live migrate the underlying storage (good if you want to consolidate storage servers, rebalance disk load, etc). with some caveats, you can do all of this without any downtime in the vm. it's not just a simple suspend on one host, resume on another host. a memory snapshot is migrated while the vm is still running on the first host, and when the amount of dirty pages starts to converge, they flip the vm over to the new host. similar idea for storage vmotion. 2. fault tolerance - for single cpu vms, you can use vmware's record-replay technology to execute a secondary vm in a "shadow" mode which replicates all of the nondeterministic events across the network. if one hypervisor host dies, the other can take over with no downtime. this is great when you need to add HA for a legacy application. 3. vsan - generally you run these systems with some sort of shared storage (nfs or iscsi attached SAN, or something like that). a SAN can be really expensive and a single point of failure. vmware can create a "virtual san" from a cluster of your esxi hypervisor hosts. as you can imagine, it has all sorts of HA features and can rebalance workloads to improve performance. there are more, but that's just a few interesting features. |