Xen has been widely regarded as the best performance VM for Linux for a long time. Oracle has been one of the advocates of Xen claiming very close to native hardware performance. # 300% improvement in UnixBench score, with a KVM Linode vs a Xen Linode # 28% faster at compiling a Linux kernel with a KVM Linode vs a Xen Linode # Boot and shutdown times are greatly improved Now Linode (one of the largest Xen sites) is moving to KVM, they list the above as benefits of KVM which surprises me. My experience of Xen is that the only way anything could be 300% faster is if it's an issue of disk IO scheduling on hard drives (as multiple virtual machines on the same spinning media causes contention and/or fragmentation issues depending on how you do it. But given that Linode was already using SSD for all storage that's obviously not what they are doing. The last time I tried KVM on my laptop the performance was a lot slower than native performance as opposed to Xen which was near enough to native hardware performance that the difference didn't matter. I've never even tested KVM on a server because the performance on my laptop (admittedly a couple of years ago) was very disappointing. Last time I tested KVM performance was not only noticably worse (EG compiles of selinux-policy-default taking about 50% longer) but the increase in CPU use was an issue of cooling. Has KVM improved a lot recently? How can anything be so much better than Xen when Xen has been so close to native performance for so long? I've just chosen KVM for a new Linode instance. They allow me to choose Xen but say that KVM is the way of the future - presumably I would be forced to use KVM sooner or later so it seemed easier to use it now. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/