

Xen vs. KVM: network, CPU, and disk performance compared - logic
http://vmstudy.blogspot.com/

======
mgrouchy
Those graphs are brutal. The graphs are 3d and on angles, so numbers that are
the same actually look different. Just a complete mess. I know thats not what
the post is about, but It makes the post considerably less useful and the
graphs considerably less usable.

~~~
tzs
Note also that it swaps the colors between Xen and KVM between the first group
of graphs and the second group. Very poor presentation.

------
sophacles
We use virtual machines to emulate larger networks, particularly when we need
true independent actors at the edges. We chose KVM over Xen because it is
easier to get an embedded system to run on emulation than it is to run on a
hypervisor kernel. Also, some systems are just not able to be hacked at in
that way. Our performance has been good, its nice to see how our intuition
shakes out compared to actual measurements.

Some notes I have on top of the article:

Network performance monitoring:

\--iperf has a tendency to use a ton of cpu. This can impact network
performance metrics. Lately I like using the 0mq performance tests, slightly
modified to last longer than the default 10s.

\--In my setups KVM adds approx .5ms latency to network transit, when using
para-virtualization through a tap device and bridge, having the host os do the
routing.

\--The virtualized e1000 works better in most cases than any other NIC KVM
will virtualize.

CPU performance:

\--The best results for KVM come when setting cpu affinity, if you have a
workload that coincides nicely to 1 vm/core, there is a performance boost.

------
Nwallins
I found it odd and jarring that for the first 2 graphs, KVM is blue and Xen is
green, while for the CPU graph, Xen is blue and KVM is green. For all
subsequent 3-way comparisons, KVM is back to blue and Xen is back to green.

------
jz
A bit off topic, but is anyone using BSD jails these days?

~~~
jolan
Nope, but I use Linux-VServer which is basically jail for Linux. It works well
with little performance penalty.

~~~
rufugee
How's your experience with vserver? I use openvz. It's ok...the technology
works, but the docs are less than desirable. I'd switch to vserver if I could
maintain the same experience.

------
doki_pen
With the way the Xen kernel has lagged, this in very encouraging. For KVM, all
that I have to do is enable it in my latest kernel sources.

