John Oliver wrote:
With VMWare and VMotion, I can understand the idea of how you can walk up to your rack, rip the cables out of a machine, and have the virtual machines be seamlessly moved to other machines. How does that work with Xen, if it's a "side by side" thing? How does Xen interact across hardware, rather than on it?
Not sure how VMWare and VMotion do it but when you migrate a Xen domain from one machine to another the Xen hypervisors on each machine communicate over the network and begin copying pages of memory from one machine to another without stopping the domain being moved. It keeps track of which pages were dirtied/changed during the copy and re-copies those. It keeps re-copying until it is no longer getting ahead and then it freezes the source domain, copies remaining pages and machine state (cpu registers, etc), then starts the copied domain on the destination machine. The freeze part usually only takes a few milliseconds so nobody notices. You can then rip the cables out of the old machine.
Are you saying that with VMWare and VMotion you can rip the cables out of a machine and THEN it seamlessly moves to another machine? I'd like to know how they do that.
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